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TOBBY OKOL ECAT Tel: 0787401800/0751269627, E-mail: tobbyecat@gmail.com
TABLE OF CONTENTS
TOPIC 1: INTRODUCTION TO COMPUTERS……………………………………..………2
TOPIC 2: COMPUTER HARDWARE……………………………………………….………47
TOPIC 3: COMPUTER SOFTWARE……………………………………………..….…….110
TOPIC 4: WORD PROCESSING…………………………………………...….……………137
TOPIC 5: SPREAD SHEET…………………………………………………..…………..….141
TOPIC 6: PRESENTATION………………………………………………..…………..……147
TOPIC 7: DATABASE……………………………………………………...………….......…149
TOPIC 8: WEB SITE DESIGNING………………………………………..……….….……156
TOPIC 9: WINDOWS ENVORONMENT…………………………………………….……166
TOPIC 10: SYSTEM START-UP AND CONFIGURATION…………………..…………174
TOPIC 11: COMPUTER COMMUNICATION AND NETWORKING……………….....183
TOPIC 12: ELEMENTARY COMPUTER PROGRAMMING………………………...…276
TOPIC 13: TRENDS IN COMPUTING………………………………………………….…285
COMPUTER ABBREVIATIONS AND GLOSSARY………………………………...……325
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TOBBY OKOL ECAT Tel: 0787401800/0751269627, E-mail: tobbyecat@gmail.com
TOPIC 1:
INTRODUCTION TO COMPUTING
Introduction to Computers
Etymologically, the term computer is derived from a Latin word “Computare” meaning a
calculating machine or a programmable machine. Therefore a computer can be defined as a
multipurpose, automatic and electronic device that allows the user to input data, store data and
information in its own memory, process input data and output information for future reference.
It is an electronic device that converts raw data into meaningful information. It can also be
described as an automatic machine made up of electronic and electromechanical device which
manipulates and processes data.
Characteristics of Modern computers
Speed
Computers are quite fast in their operation in that their speed is measured in Millions of
Instructions per Second (MIPS) or Megahertz (MHz). Inside the computer's system unit, the
processing occurs through electronic circuits. Data and program instructions travel through these
circuits at speeds close to the speed of light. Many computers process billions or trillions of
operations in a single second.
Accuracy
Computers are known to be accurate. They can process large amounts of data and generate error-
free results, provided the data entered is correct. They hardly make any mistake. They are
capable of detecting and correcting any mistakes made. It follows therefore, that if wrong data is
fed into the computer, the resulting output will be incorrect.
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Storage
For a computer to be able to work it must have a work space where data is stored before being
processed or where information is stored before being output to particular devices. This storage
space is known as Memory.
Automation
Computers work automatically. They do not need any supervision in order to perform
programmed routines. This is because of the instructions (programs) installed in them.
Diligence (Consistency)
Computers have the ability to perform the same task over and over for neither a long time
without getting bored and with nor mistakes (errors).
Artificial intelligence
Computers are artificially intelligent. They can respond to requests given to them and provide
solutions. This is because of the programs installed in them. Evidence is seen in industrial
Robots.
Versatility/Flexibility
Computers are capable of performing different kinds of tasks provided the specified task is
followed in a proper order.
Basic Parts of a Computer
A computer is made up of a collection of different parts that are interconnected and working
together in order to function a single entry.
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Monitor
A monitor is a display device that looks like an ordinary television screen used for displaying
information in visual form such as text, graphics, still and moving pictures. There are two types
of the monitors: cathode ray tube (CRT) monitors and Liquid crystal display (LCD) monitors.
Without a monitor, it is very difficult to see what you enter into the computer
Keyboard
A keyboard is a primary input and control device of a computer that allows the computer user to
enter data and commands into the computer. It has a typewriter area that looks like or similar to a
typewriter keyboard.
Mouse
This is a handheld input pointing device that controls the movement of a pointer on the screen. It
is a device used to point and select items on the computer screen. It is small, oblong and
connected to the system unit by a long connecting cable. It is an extension of your hand since
you cannot touch inside the computer.
System unit
The system unities a rectangular box-like case placed on or under the table that houses both
internal and external electronic components of a computer.
Factors to consider when acquiring a computer
The cost of the computer
The storage capacity
The processing speed
User needs
Portability
The monitor size
Connectivity
Maintenance cost
Availability of hardware and software in the market
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System requirements
Multimedia capability
Terminologies and concepts applied to computing today
There are many terminologies used in the field of computing. Below are some of the basic ones:
Computer studies: This is a subject which deals with the features of computers, ways and
methods of using computers so as to provide a basis for understanding the impact of
computers on individuals, organization and society.
Computer literacy: computer literacy is the nontechnical understanding of microcomputer,
how to use simple applications and of the role played by computers in the society. Computer
literacy includes an awareness of computers, knowledge about computers and interaction
with computers.
Notice: Awareness means being aware of the importance, versatility and the potential of
computers for their good and ill in the society. Knowledge, means learning what computers
are and how they work. Interaction means learning to use computer for some simple
applications.
Information Communication Technology (COMPUTER): This is the combination of
telephone lines, computers, hardwires and software which enable users to create access,
store, manipulate and transmit information.
Information Technology (IT): This is the study that involves the software and hardware to
design, implement and support a computer-based information system.
Data: Data refers to raw facts and figures that are processed into information. Examples are
numbers, exams scores, musical notes, words, and symbols etc.
Data entry
It is the act of in putting data into the computer. This is done by the help of input devices like
keyboard, mouse etc.
Information: Information is the processed data which is organized, meaningful and useful. Is
manipulated/ processed data e.g., Apple, boy, cat, report, letter, comments, grades etc.
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Byte
A byte is a unit of computer memory or digital information that consists of eight binary digits
(bits).
NB. 1 byte stores 1 character.
Binary
The number system used to represent digital information in computers where data is expressed
by combinations of the digits 0 and 1, corresponding to power states "off" and "on" respectively.
Computer Memory
This is a store for digital Data, processed information and programs in a computer system.
RAM (Random Access Memory) is temporary and volatile working memory that contains all
the work in progress, since the user last saved to disk. RAM changes constantly as the computer
is used for different tasks and is lost when the computer is switched off.
Reasons why we study computer in secondary schools
1. To acquire general knowledge and skills in the use of computers and related technologies.
2. To use the acquired knowledge in computer studies to enhance learning other subjects.
3. To understand important issues of a technology based society and exhibit them using
computers.
4. To exhibit basic computer skills that is required for employment.
5. To acquire knowledge as a foundation for further studies in computer technology.
6. To use a variety of computer technologies to assess, analyze and interpret information.
7. To promote creative knowledge for problem solving such as multidimensional problems
that requires imagination and sensitivity to a variety of fields
8. To promote critical and analytical thinking for proactive (hands-on) solution such as
vaccine research, environmental protection, business, entertainment and education.
9. To create awareness in learners about the developments and emerging issues concerning
computing and society
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10. To get jobs such as computer operators, Computer technicians, System analysts,
Computer programmers, Software engineers, Computer engineers, Database
administrators, website masters, Graphic designers, IT Teachers, etc.
History and evolution of computers
The word Evolution comes from the Latin word, ‘ēvolvō’ which literally means; to ‘unroll’, or to
‘unfold’.
Evolution of computers refers to the historical developments through which computers and
technology have passed, from the time they started to exist in ancient forms to their current state.
Knowledge about the history/evolution of computers gives us a deeper understanding of the
origin and the gradual Mechanical to Electro-mechanical to Electronic technological changes,
which have brought about the kind of computers we see today, and helps us to predict Computer
how they will be in future.
Origin of calculation
Although electronic computers have become popular in the past 4-5 decades, man had
always had the urge to solve problems and manage information/data in a much easier way.
As a result, various mechanical devices were invented by man to help him fulfill his needs.
So the origin of computing started with the early man who used fingers, stones, sticks, marks on
walls, sand, etc.
The word ‘compute’ was derived from two Latin words; ‘com’, which means ‘together’ and
‘putare’, which means ‘add, calculate, count, or estimate’.
Over the centuries, people have developed an amazing variety of data processing tools and
techniques. Some of these devices could not work on their own they required some human
assistance in order to carry out their tasks effectively
Examples of ancient counting and calculating devices include: The abacus, Napier’s bones, the
Slide rule.
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Calculation era
The Abacus
Napier Bones
Slide Rule
Abacus (3000BC)
This was the first computing device used in the 16th Century in China and Japan to compute
volume for thousands of years Before Christ.
It consisted of a rectangular wooden rack which had horizontal wires running from left to
right. Theses wires had beads stuck on them. It is these beads that were used for simple
addition and subtraction.
Napier’s bones (1617)
It was invented by a Scottish Mathematician called John Napier in1617. It was made of ivory
rods which looked like bones and they had numbers painted on them.
It was used to solve mathematical problems involving multiplication, subtraction, division and
addition. This could be done by sliding the bones back and forth.
Slide rule
Slide rule was invented by British mathematician called William Oughfred in 1620 as the first
kind of analog computer. This device was made up of two sets of scales marked in logarithms.
This Mechanical Computer could also solve mathematical problems involving multiplication,
division, addition and subtraction. All these computations could be done by sliding its cursor.
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Mechanical era (1623 – 1945)
Before 1642, all computation was done by humans. Manual devices used then could just aid the
users to keep track of numbers as they did the computing.
In the Mechanical Era (Period) however, machines and gears did the computations. This era also
saw the development of the world's first computer programmer Ada Byron Lovelace (1815-
1852)
The popular mechanical developments of computers in this period include:
Blaise Pascal's Calculator (1642)
Leibniz’s Stepped Reckoner (1694)
Jacquard’s Loom (1801)
Charles Babbage’s Analytical & Difference Engine (1834).
Hollerith’s Tabulator (1860)
Blaise Pascal's Calculator (1642),
Blaise Pascal calculator was invented in around1642 by Blaise to help his father who was a Tax
Collector to simplify his calculation from the taxes collected daily.
It was the first mechanical adding machine which used a system of gears and wheels. It consisted
of toothed wheels which were numbered from 0-9. When one wheel moved past the notch of
another wheel, it would cause it to rotate automatically.
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Leibniz Stepped Reckoner(1694)
The Stepped Reckoner was a digital mechanical calculator invented by German mathematician
Gottfried Wilhelm Leibniz around 1672 and completed in 1694.
It was the first calculator that could perform all four arithmetic operations: addition, subtraction,
multiplication and division including square roots.
Jacquard Weaving Loom (1801)
Jacquard weaving loom was developed by Joseph Marie Jacquard of France in1801 who made
the first successful automatic draw loom by means of a series of instructions given to the threads
by a punched card system.
It was a textile weaving equipment whose instructions were stored on punched paper cards.
These instructions could automatically control this machine. He developed it with the intention
of devising means of simplifying the weaving process of complex patterns within the textile
industry.
Babbage’s Analytical Engine and Difference Engine
Charles Babbage from England is considered the first person to propose the concept of the
modern computer hence called the Father of Computing who partially invented two machines
that is different and analytical machines.
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Difference Engine
In 1823, with the help of a grant from the British Government, he partially built a steam driven
mechanical calculator called the Difference Engine to compute logarithms tables.
Analytical Engine
He then thought of an Analytical engine which was a mechanical steam driven mechanical
machine which had many characteristics of a modern computer such as input, storage, control,
mill, and output. It uses punched cards to restore its data and instructions.
The First Computer Programmer
Lady Augusta Ada Byron Lovelace (1815-1852) is the first world computer programmer.
In 1842, Ada was asked to write a scientific interpretation of the Analytical Engine and its
operations. These extensive writings on the Analytical Engine later became known as the first
explanation of computer programming.
Notice; In between 1890 to 1946, there were another three inventions that took place. Among the
popular developments of computers within this era include;
Hollerith's tabulating machine (1890)
Howard Aiken’s Harvard Mark I (1944)
Program “debugging” (1944-1946)
Hollerith’s Tabulator
Dr. Herman Hollerith (1860 –1929) was an American statistician who developed a mechanical
tabulator based on punched cards to rapidly tabulate statistics from millions of pieces of data.
He decided to use punched cards to represent the data gathered for the USA population census of
1890, and to read and collate this data using an automatic machine.
Hollerith’s machine used a set of spring loaded wires suspended over the punched card reader.
When the wires were pressed onto the card, punched holes allowed wires to complete electric
circuits. The cards were coded for age, state of residence, gender, and other information
It was a hand operated computer which used punched card for storing and tabulating data. It
allowed the 1890 US census to be completed in less than three years.
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It is said that before the introduction of this computer, it had taken the Bureau seven years to
compile the results but with this computer, it took the Bureau few months to compile the
results of 1890census.
He then left the census Bureau to start a business Firm (company) to produce punched card
machines. He called his company Dr. Hollerith’s Tabulating Machine Company. He later
named it the International Business Machine Corporation (IBM), the present day computer
manufacturer.
Howard Aiken’s Harvard Mark I (1944)
Howard Aiken Harvard Mark was a professor at Harvard University who was supported by IBM
to build an electro-mechanical computer which began computations for the U.S. Navy Bureau of
Ships.
The computer was called the Automatic Sequence Controlled Calculator – (ASCC) by IBM but
Harvard renamed it the Mark I.
It was very reliable, much more so than early electronic computers. The computer had
mechanical relays (switches) which flip-flopped back and forth to represent mathematical data.
It was huge, weighting some 35 tons with 500 miles of wiring.
The First Computer Bug
Dr. Grace Murray Hopper was a lady in the U.S. Navy Bureau of Ships, who worked with
Howard Aiken from 1944 and used his machine for gunnery and ballistics calculation
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One day, the program she was running gave incorrect results and, upon examination, a moth was
found blocking one of the relays.
The bug was removed and the program performed to perfection. Since then, a program error in a
computer has been called a bug.
Debugging is a process of finding and correcting errors, in a computer program or a piece of
electronic hardware.
The Electronic era
The electronic computer generations
A computer generation refers development and accumulation of computer technology over
the years. Computers have gone through five (5) stages during their development each
generation is characterized by dramatic improvements in;
Technology to build the computer
Internal organization of the computer
Programming languages used.
The physical setup of computer i.e. the size
Increase in performance capabilities
The setback of the computers
FIRST COMPUTER GENERATION (1946 – 1956: vacuum tube)
Technological innovations
Vacuum tubes which were used for power distribution and internal operations
Magnetic drums which were used for storage
Punched cards for input and output
Characteristics of first computer generation
They had limited primary memory, a maximum of 2000bytes (2KB) of RAM
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Programming was done in machine code.
They had a speed of 10 kilo instructions per second.
They consumed a lot of power.
They gave off a lot of heat.
They were very expensive
They had maintenance problems and needed a stand by technician.
They were very heavy (about 30tons)
They were very big (almost of a size of a room)
They had no operating system.
Examples of first computer generation
ENIAC (Electronic Numeric Integrator and Computer)
UNIVAC (Universal Automatic Computer)
EDVAC (Electronic Discrete Variable Automatic Computer)
IBM 650 (International Business Machine)
SECOND COMPUTER GENERATION (1957 – 1963: Transistor)
Technological innovations
Transistors which were used for power distribution and internal operations
Magnetic core memories for storage
High level programming languages such as FORTRAN (Formula Translation,
COBOL (Common Business Oriented Language)
Super computers such as LARC and IBM 7030
Characteristics of second computer generation
Speed of operation increased to 200,000 – 300,000 instructions per second.
They generated less heat and consumed less power compared to their predecessors.
They became more reliable compared to the first generation computers.
The computers became smaller in size.
Computers became less expensive.
They had no operating system.
The primary memory increased to 32KB of RAM
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Examples of second computer generation
NCR 501
CDC – 6600 mainframe computer
IBM 7030
TRADIC
IBM 7030
LARC (Livermore Atomic Research Computer)
THIRD COMPUTER GENERATION (1964 – 1979: Integrated circuits)
Technological innovations
Integrated Circuits (ICs) for power distribution and internal operations
ICs were made by combining several transistors onto a single chip
Magnetic disks for storage
Production of the first mini computers
Introduction of the first operating systems
Characteristics of third generation computers
Introduction of simple programming languages like BASIC (Beginners All purpose
Symbolic Instruction Code)
Computers greatly reduced in size compared to their predecessors.
Computers became reliable, smaller in size, cheap and consumed little power
which made them popular.
The keyboards and monitors replaced punched cards for input and output.
Magnetic hard disks were developed for storage purposes
Memory size expanded to approximately 2 megabytes of RAM
Speed increased to 5 million instructions per second
Integrated Circuits consumed a lower electric power.
The noise produced by the computers reduced drastically
Examples of third computer generation
IBM 360 series
IBM 370
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A microprocessor
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PDP-11
8-bit microcomputers
FOURTH COMPUTER GENERATION (1979-1989: Microprocessor)
Technological innovations
Development of the Large Scale Integration Circuits and
Very Large Integration Circuits which led to the invention of
microprocessor
Development of the first microcomputers
Characteristics of fourth generation computer
Introduction of microprocessor that led to the development of micro and mini computers
Introduction of 404 Intel chip
Primary memory increased in size to 128MB of RAM
The speed accelerated to 50 million instructions per second
Computers became more powerful and cheap
Introduction of robotic technology
There was limited artificial intelligence and expert system
Introduction of a wide variety of software
Development of programming languages which are easy to use which resemble
human languages like C, C+, C++ etc.
Direct use of input and output devices like keyboards, mice etc to provide a more
natural user interface
Examples of fourth computer generation computers
Mainframe computers such as; IBM308, and Amdah580
Computers with processors 8088, 802886, 80386
Apple Macintosh
FIFTH COMPUTER GENERATION (1990 – Present: Artificial intelligence)
Technological innovations
Use of artificial intelligence
Production of Robots
Characteristics of fifth computer generation computers
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Development of powerful and intelligent computers with the ability to see, listen, talk
and think started.
Innovation of biometric systems
Development of wireless communication
Increased use of wireless communication through the use of mobile phones
Computer hardware and software costs and sizes decreased drastically.
Development of networking technologies
Emerging telecommunication and computing technology
Use of Very large microprocessor circuits in parallel processing
Use of highly sophisticated operating systems
Innovation of CCTV for security purposes
Introduction of flash memory for data storage
Use of robots most especially in industries
Artificial Intelligence is a group of related technologies that attempt to develop machines
to emulate human like qualities such as learning, reasoning, communicating, seeing and
hearing.
Artificial intelligence includes:
Games playing: programming computers to play games such as chess and checkers
Expert Systems: programming computers to make decisions in real-life situations
(for example, some expert systems help doctors diagnose diseases based on
symptoms)
Natural Language processing: programming computers to understand natural
human languages
Neural Networks: Systems that simulate intelligence by attempting to reproduce the
types of physical connections that occur in animal brains
Robotics: programming computers to see and hear and react to other sensory stimuli
Computers of preceding/former generations.
Computer Generations and associated technologies
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Generation Technology
First Generation Vacuum tubes
Second generation Transistors
Third generation Integrated circuits
Fourth generation Microprocessor
Fifth generation Artificial Intelligence
Uses of computers in the society
Below are some of the fields where we come in contact with computers.
1) Education
2) Research
3) Business
4) Health
5) Communication
6) Security/ Military
7) Home
8) Entertainment / leisure
9) Bank
10) Industry
11) Government
12) Transport
13) Farming
14) Supermarkets
Education
Education is one of the fields in society where computers have a wide-spread usage.
Students use computers and appropriate software to learn at their own pace. This learning
is known as Computer Assisted Learning (CAL).
Computers are use as learning aids.
Through use of computers and internet, distance learning has been possible.
Computer are use for educative entertainment
They are used by researchers to quickly gather and analyze experimental data.
Students are using computers to do school- related tasks like designing posters during
campaigns, publishing school newsletters etc.
Teachers are using computers and other related IT equipment to present teaching
materials in a more interesting way.
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They use them to do internet research and enrich their notes or to keep up to date
information
In the advanced education systems, teachers use computers to deliver their lessons.
Teachers are using computers to compile and analyze student’s performance.
Computers are used to simulate experiments and other real life situations by teachers.
Computers are used in school libraries to take record of the stock of books and the
borrowers of the books.
School bursars are using computers to compile data concerning finances and payments of
institutions’ students and staff.
Organizations such as examination boards are using computers to mark answer scripts.
Most schools today are adopting the school administration and management systems
(SAMS) for keeping records about students and producing report cards and other related
documents.
School secretaries are using computers to quickly produce exams, and other
administrative documents.
School administrators are using computers to keep records of the employees personal
data
School administrators are using computers for communication purposes
Computers that are connected to internet have enable teachers and students to have access
to education information.
Computers have simplified registration of candidates more easily through e-registration.
Research
The use of computers have made searching the literature and references easier through
use of electronic databases on the World Wide Web.
Computers have tools such as Spell checking, cut-and-paste, etc., which make compiling
and editing research work easier.
Computers have a lot of statistical software available for performing calculations and
analysing the collected research data.
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Computers allow data obtained from the research to be easily stored in softcopies as word
documents or excel spread sheets.
Computers allow research work to be converted to Portable Document Format (PDF) and
published to the World Wide Web.
Business
Computer has enable e-commerce business trisections to take place.
Computer has played a very important role in effective management and running of
business activities such as data management and data processing.
Computer has enabled easy calculation and decision making capabilities in the
commercial world.
Computers gadgets are helpful in inventory control and management in business
especially in good stocking, storage details and goods distribution.
Computer has enables business sectors to carry out advertisements and marketing of
goods and services.
Computer has enable customer care and services possible for example the use of Toll free
mobile communications for customers with the service providers. For instance may
business companies use SMS (Short Messaging Services) to reach out to their customers
Computers are very important in accounts and Pay roll management.
Business premises are using computer equipments to enhance their security for example
the use of CCTV cameras, sensor, voice recognition equipment, smart cards etc.
Business companies can use the internet to carry out research on quality and genuinity of
products.
Health
Computers are used to maintain patient‘s records in hospitals, clinics and other health
centers.
Computers are used to monitor patients ‘vital signs in hospitals, at home and clinics.
Computers are used to carry out computer – assisted medical tests in clinics and
hospitals.
Computers are used in diagnosing medical conditions of patients.
Doctors and other medical workers are using computers to carry out research about new
medicine and diseases.
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Computers are used during implanting of computerized devices (i.e. Pace makers e.g.
heart) that allow patients to live longer.
Computes are used to control computer – controlled devices that require great precision
during operations such as laser eye surgery and heart surgery.
Computers are used by experienced doctors and surgeons to train others through
computer – aided surgery prior to performing surgery on live humans.
Modern hospitals and health centers are using computer assisted technology in baby
incubators to artificially grow babies.
The security of the hospitals, properties, and the patients is ensured by high end computer
devices such as CCTV cameras, sensors etc.
Communication
In telecommunication industry every telephone exchange relies on computers to switch
incoming and outgoing calls.
In the multimedia industry such as TV stations, Radio station, program managers keep
computer terminals on their desks to record urgent and important news.
E-mail: Electronic Mail sent from one person to another using connected computer helps
a lot in the area of communication.
Tele Conferencing and Video Conferencing enable people in different locations to
conduct meeting as if they are in the same location
Computers are used for Faxing that is sending an image of a document electronically.
Computers are use to send voice, image, text and data though Telephones and mobile cell
phones
Large population are using computers to communicate to one another via social network
such as face book, what sap, twitter etc
Security
Computers are highly used in fighting against crime by using digital forensic
(investigation involving crime scene) and CCTV cameras.
Security officers are using computer related devices such as Biometric devices to
identifying criminals.
Computers are highly used by army by gathering electronic news, detecting and tracking
of gadgets by using radar systems, warning systems and military laser.
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Computers are essential in online communication by the military agencies
Computers are used in training and educating military forces especially with skills and
vital details regarding military tactics.
Computers are used to design and to test new security system
Security agencies use the phones and internet tapping techniques to track down crimes.
Traffic Police uses computer-controlled traffic lights to control traffic flow and speed on
the roads by using speed sensors to find over speeding drivers.
Homes
Many people are using computers for shopping purposes because they provide them
with lists of shopping items as well as prices and electronic fund transfer facilities.
People use computers in homes to pay bills through the payment by phone services
(PPS).
People use computers for education and research from home example online studies
People use computers in homes for communicating with friends and relatives via e-
mails, telephones, chat rooms, etc.
Many people are using computers to store family records such as names of family
members, family background, etc.
Computers are used by students and other learners in doing home assignments.
Entertainment
Computers are used to play music.
They are also used to play movies and videos which help in entertaining people
People use computers in playing modern computer games such as solitaire, Tetris, Free
Cell, Packman etc.
Computers are used in composing and editing video and audio clips.
Computers are also used in Cinema halls and podiums for faster instant audio and video
playback and presentation though projectors.
Bank
The use of computer related device like ATM (Automated Teller Machine) has enable
clients to draw their money with a lot of ease; ATM allows client to;
Make deposits of cash and cheques
Withdraw cash
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Transfer money between accounts
Obtain account balances.
Computers are used to carry out online banking. They are used to transfer money
electronically among different accounts, apply for loans, and obtain bank statements,
account balances and credit card statements.
Computers are use for keeping record of all the banks’ clients in terms of their personal
data, account numbers, and their deposits and withdrawals on their respective accounts.
Computers are used to run Magnetic Ink Character Recognition (MICR) to process
cheques.
They are used to run microfilm and microfiche to store transaction records.
Computer related device like counting device is use for counting notes (money).
Computer related device such as CCTV cameras and sensors are use to ensure security in
banking environment.
Industry
Computers of all kinds are widely used for the daily operations in industries.
In Manufacturing Industries/Factories, Computers are used to make the production and
sometimes packaging processes faster.
Computers are used for online communication with different industries and businessmen.
Computers are used to manage large volumes of financial transactions within the
industries.
Computer driven machines such as robots are used to carry out repetitive tasks, lift
heavy equipment, and carry out tasks which require a high degree of precision.
They are used for research about new stock especially through the use of the internet.
Government
Computers are highly used in many government ministries such as finance, education,
etc, to store government records.
Computers are also used to improve the efficiency of work within the civil service.
Computers are used for easy communication between governmental institutions.
They are used for easy planning and budgeting for governments.
Computers are use to carry out statistical analysis of data such as population census bio
data
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Government is using computer related devices such as CCTV to monitor all the
government premises for security purposes.
Computers have enabled the government in creating a national data base bank such as
that of national IDs, country population, number of civil servants, and number of students
in both government and private institutions for proper planning.
With the use of computer, the auditing department of government can easily monitor
public expenditure and finance in various government agencies.
With the use of COMPUTERs, the national electoral commission is able to carry out
democratic process such as national voter registration exercise, designing and printing of
voters cards and in coordinating of the tallying exercise nationally.
Transport
For Air transport, computers are used at the airports to take record of all the flights and
passengers for each and every place that will fly off or land at that Airport.
Used for security check-Ups at the Airports, e.g. to check whether one is smuggling in
or out weapons for war, drugs, etc.
While inside the Aeroplane, computers are used to give the pilot sense of direction by
indicating how high he is flying, the temperatures, the pressure and weather conditions
of the space in which he is flying. They also show some physical features which could
obstruct the planes movements.
In the cars, there is speedometer, which determines the speed at which the car is
moving.
Computer related devices especially satellite is use for tracking the lost cars
In a ship, computers are used to guide the captain movements while he sails. By
showing the landscape of the sea bed, the captain is able to draw the right direction and
bearing in which he should sail the sheep.
Farming institutions
Computers are use for keeping records of farm, customer details and sales.
Computers connected to the internet are use for carrying out research about new
technology in farming.
Use of mobile money services in paying and receiving payment for goods and services by
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the farmers or farming institutions
Computers are use for branding of farm products.
Super markets
Use of bar code reader in reading serial numbers on packaged products.
Creating a data base and keeping customers records.
Computer related device like counting device is use for counting notes (money).
Use of CCTV cameras and sensors in ensuring security in the supermarket.
Computers are use for creating and printing customer receipts after purchase of items.
Computers are use for inventory management such as stock taking.
Computer care and safety
The computer laboratory
A computer laboratory is a room that has been especially prepared to facilitate installation of
computers and to provide a safe conducive environment for teaching and learning computer
studies. This is a place where computers are set for a particular task. While in the laboratory a
teacher should work closely with students to see that they master basic techniques.
Computer Literacy
Computer literacy is the nontechnical understanding of microcomputer, how to use simple
applications and of the role played by computers in the society.
It is the knowledge and ability to use computers and related technologies with a range of
skills covering levels from elementary use of programming and advanced problem solving.
The major goal of computer literacy is to promote the information culture, abstract
thinking, and ability to use computer skills for professional purposes in the future.
Computer literacy includes an awareness of computers, knowkedge about computers and
interaction with computers.
Awareness that is being aware of the importance, versatility and the potential of computers
for their good and ill in the society
Knowledge; learning what computers are and how they work
Interaction that is learing to use computer for some simple applications
Goals of computer Literacy
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To enable people to learn and use computer programs with minimal help. To enable people of all ages an edge in both their career and education To expose knowledge and skills To employ in formations To express ideas compellingly To act ethically
Computer literacy involves having both the basic skills & intermediate skills.
Basic skills include;
Ability to start / switch on a computer (boot) Ability to use the mouse & interact with screen objects Being able to use the computer key board Ability to open & locate files Ability to shut down a computer properly. etc
Intermediate skills include;
1. Functional knowledge of word processing2. Functional knowledge of spreadsheets3. Functional knowledge of presentation software.4. Ability to use the email5. Ability to use the internet 6. Ability to install and uninstall software.
Computer Laboratory equipments and tools and their functions
Air conditioner: Regulates room temperature Bugler proofing: Prevents unauthorized access in the computer
laboratory. Woolen carpet: Absorbs dust & Shock. Toolkit: Used to store necessary tools required for computer
maintenance. Dust blower: Used to blow off dust from system unit components. Routers, modems gateways: connect the computers to the network.
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A gaseous fire extinguisher: To prevent fire from spreading in case of a power outbreak.
Surge protector: This is an appliance that protects a computer from voltage spikes.
Curtains: These protect computers from direct sunlight. Dust covers: these are pieces of clothes covered on the computers after use
to prevent dust. Anti glare filters: these are covered onto the monitors to reduce on the
effect of bright light onto the retina. Water proof covers: Safeguards computer hardware from contact with
water & moisture Lightening conductor: prevent lightening from striking the computers. CCTV camera (closed circuit television camera): Monitor security of the
laboratory. Mouse pads: allows proper movement of the mouse as well as preventing
dust from entering the mouse sensor. Factors to consider when preparing a computer laboratory
Security of computer programs and other resources.
Reliability of the source of power
The number of computer to be installed and the available floor space.
The maximum number of users that the laboratory can accommodate.
Availability of fire fighting equipments
Availability of first aids kit
The room should be well ventilated
The room should be dust free environment
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Typical computer laboratory
After establishment of the computer laboratory the number of safety precaution and practices
need to be observed in order to avoid accidental injuries to users, damage or lack of Conducive
environment for teaching and learning.
Safety precautions are measures to be put in place to prevent damages of computers and
equipments meanwhile safety practices are activities to be perform regularly to prevent damages
in the computer laboratory.
Therefore the following safety precautions and practices must be put into considerations;
1) Physical securityThis involves all activities done to eliminate the physical access by unauthorized people into the computer laboratory.
Ways of ensuring Physical security
1. Burglar proofing the lab.2. Locking the laboratory with a strong lock3. Employing a Security personnel4. Backing up information both onsite & offsite5. Installing an Alarm security systems6. Limiting access to computer ports
2) Software security
This involves all activities done to prevent computer software from being damaged by viruses and accessed illegally by hackers.
This can be done by;
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a) Installing a strong Antivirus
b) Installing Anti spy ware
c) Installing Firewalls
d) Creating passwords
e) Separating users accounts
f) Software updating and upgrading
3) Electric power securityUnstable electric power supply can lead to damaging of electric equipments.To prevent damage due to electricity;
1) Use of surge protectors2) Use of uninterruptible power supply3) Providing a standby generator4) Use of good quality strong cables to connect computers.5) Proper insulation of cables to avoid the danger of exposing the users to
electric shock and power interruption.6) Connect all devices which use electricity to power regulators. These
regulators include; Uninterruptible Power Supply (UPS) Stabilizers etc. 7) Make sure that the sockets, extension cables, power cables and other
related electrical gardgets are properly connected and they are in good working conditions.
8) Also avoid over loading of sockets and having very many devices plugged into a single power outlet.
N.B .The major functions of ups are;
It regulates the amount of power entering into the device. To safely turn off the computerTo temporarily supply power to enable the user to complete work at handTo supply power to continue working when power goes offIt provides a power backup which can keep power for some time.
Fire outbreak in the computer labTo prevent fire from catching other equipments, the following should be place in a
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computer lab;1) Fire extinguishers2) Smoke detectors3) First aid boxes 4) Air-conditioning.
Causes of fire outbreak in the computer labShort circuits due to Poor wiring of electric cablesUnstable power supplyPouring water onto the electric socketsPoor quality power cablesThunder strike / lighteningUnnecessary moving of equipment in the laboratory
Ways by which fire accidents can be prevented laboratory.a) By proper wiring of electric cables to prevent short circuitsb) By Installing power surge protectors such as UPS c) By Installing a lightening conductor on the laboratoryd) By avoiding food and water in the computer laboratorye) Avoid using computers during heavy rains.4) Security cameras (CCTV)
Installed Video surveillance systems inside and outside the computer lab to monitor and record criminals who vandalize or steal from the computer lab such as CCTV cameras (closed-circuit television) is a video camera that transmit a signal to a specific place on a limited set of monitors.Consider installing a security alarm at a strategic point in case of a breakage.
5) First aid kit
A first aid kit or first aid box is a collection of supplies and equipment for use in giving first aid to computer users in case of any accident during computer usage. so;
It is recommended that all kits are in a clean, water proof container to keep the contents safe and aseptic.
Ensure that the first aid kit has all the contents such as adhesive 30
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bandages, regular strength pain medication, and low grade disinfectant. First aid kits must be checked regularly and restocked if any items are
damaged or expired.6) Fire extinguishersFire extinguisher is a portable device that discharges a jet of liquid, foam or gas to put off fire. It is normally filled with carbon dioxide gas which is used to extinguish fire.
Ensure that fire extinguisher is fixed in the computer lab in case of any emergency fire outbreak.
It is essential to always refill the fire extinguishers after a stipulated period of time.
It is also essential that all computer users are taught how to use fire extinguishers.
7) Air conditioningAir conditioning is the process of changing air temperature and humidity within an area to amore comfort condition. The machine used to modify the the air condition of a place is known as Air Conditioner or Air Con (AC). It is a machine designed to change air temperature and humidity within an area to a more comfort condition. It is used for cooling as well as heating depending on the air properties at a given time.
Ensure the installation of air conditioner to regulate temperature.
There must be a good air circulation in the computer room to avoid suffocation and overheating
Ensuring that the room has enough ventilation points like windows.
Avoiding overcrowding of either machine or users
Ensure proper ventilation to avoid damage by overheating The room must be well lit to reduce eye strain that eventually leads to
headache, stress and fatigue. Over bright wall paints reflect too much light causing eye strain.
Data risks in the computer laboratory
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1) Data theft
2) Virus attack
3) Erroneous deletion of files
4) Failure to save files
5) Information theft and piracy
6) Cracking of software.
7) Damaging of the storage media
Ways of safeguarding data in a computer lab
1. Protecting files with a password
2. Backing up of data.
3. Separating users accounts on the computer
4. Installing strong antivirus software.
5. Scanning all storage media before opening them
How can a computer lab be safely used?
1. Plug all computer equipments into a surge protector to avoid power spikes and surges in electrical power which can damage the electrical equipments.
2. Set up a network layer firewall.
3. Setup weekly updates or weekly updates
4. Install an up-to-date anti-virus soft ware.
5. Back up your computers on regular basis.
6. Use the hard disc clean up and defragmentation utilities regularly.
7. Dust the computer screens regularly with a thin soft microfiber cloth
8. Clean the computer lab regularly
Computer laboratory rules and regulations
1. Do not open inside part of computer when cleaning, this should be done by a trained
personnel.
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2. All CDS used for installation of programs and backups should be kept safely in Disk banks
and away from sun shine and magnetic media.
3. In areas where power fluctuates it is important to use a stabilizer or UPS to ensure steady
input power to the computer system.
4. Peripheral devices like printers should be serviced regularly.
5. Installation and updating of an antivirus should be done regularly.
6. All foreign storage devices like floppy disks, flash disks, and external hard disks should be
scanned from computer viruses.
7. Backup copies should be done regularly to ensure that there is no data loss made.
8. If you have unwanted copies of print outs these should be destroyed because data is not
supposed to fall in unauthorized hand.
9. Always lock up all the premises where computers are kept to prevent theft and intruders.
10. Minimize the number of user/visitors to your installation and do not allow any outsider to
your server apart from network administrator.
11. Always keep important information with passwords.
12. Never leave computers on after use and you should follow the systematic way of shutting
down.
13. Playing of computer games are prohibited from the lam.
Care for computer user and ergonomics
There are a number of health problems that are associated with improper and too long use of
computers and its related devices.
1. Musculoskeletal problems:
Muscle soreness and muscle fatigue are the most common complaints of regular computer users.
Back pain, chest pain, pain or numbness in arms, shoulder and feet top the list. These types of
problems mainly occur because your posture while using the computer is not correct. Either you
are sitting on an uncomfortable chair or your workstation is not supportive of correct posture.
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Practical tips
Adjust your chair and desk such that your screen is either at your eye level or lower. Sit with
your back straight and legs perpendicular to the floor with feet resting flat on the floor. Your
elbows should rest at the sides.
Take mini breaks from work and stretch a bit or go for a short walk.
2. Repetitive stress injury
Pain in the neck, shoulder, or anywhere from the shoulder to fingers may indicate repetitive
stress injury. When you use your muscles in an awkward position, you may experience stiffness,
pain or swelling in that area. For example, twisting the wrist to use the mouse or specific typing
technique that causes stretching of fingers or pressure on the wrist can turn really painful. One of
the disorders that affect the fingers and wrist is carpal tunnel syndrome.
Practical Tips:
Adjust the mouse besides the keyboard. Move your entire arm, while moving the mouse.
Don’t just move your wrist by fixing it at one position. Typing should be gentle. Do not fix
your wrists in a certain position while typing.
Relax your arms or stretch when you are not typing or using the mouse.
3. Vision problems
Bright light and bad glare or flickering image can strain your eyes. Constantly focusing on the
screen without blinking can cause dry eyes. Computer vision syndrome is another problem that
you may suffer from.
Practical tips
Adjust the contrast and brightness such that your eyes are not strained. You can tilt your
screen to avoid glare.
Maintain a proper distance from the screen. Look away from the screen intermittently.
Don’t forget to blink.
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4. Headache
Because of increased muscle tension or pain in the neck at the base of the skull, headache is
common problem with computer use. Many a times, prolonged use can affect eye power which
needs vision correction. This can also result in headache.
Practical tips
Get your eye power tested if headache is a common problem with computer use.
Keep your neck straight when in front of the computer. Constantly looking down or
stretching the neck sideways can also cause pain. Take breaks in between and circle your
neck a bit to release the strain.
5. Obesity
Studies have shown that prolonged use of computers, especially in children, is the major
contributing factor of sedentary lifestyle and childhood obesity.
Practical tips:
Set limits for your children if they insist to playing computer games non-stop.
Encourage your children to play outdoor games or to take up a hobby. Involve them in extra-
curricular activities
Adults who work for 7-8 hours should avoid spending time on computer after reaching home.
Your body and mind both need to relax. Join a gym or go for evening jog and stay physically
active.
6. Stress disorders
Technology has a huge impact on our behavior and emotions. Prolonged computer use along
with other factors like poor health, work pressure and job environment can make you susceptible
to stress. Moreover, the longer you uphold the stress, the more susceptible you become to other
health issues mentioned above. It can also lead to loss of concentration, dizziness and weariness.
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Practical tips:
Be proactive and take necessary measures to beat stress before it affects your health.
Computer ergonomics
Computer ergonomic refers to the study how people interact with computer, its related devices
and all aspects of the working environment.
Computer ergonomics includes;
Furniture design
Equipment placement
User techniques
Hardware and software designs
Total working environment
Servicing and maintaining of computers
Computer servicing refers to the act of supporting and maintaining computer such as installing, maintaining, configuring, and diagnosing computer systems and networks meanwhile Computer maintenance is the practice of keeping computers in a good state of repair. Servicing and maintaining of computers involve the following practices;
Install Antivirus Software. ...Perform Regular Software Updates. ...Keep Your Keyboard Crumb Free. ...Use a Surge ProtectorBack up data.Cleaning dust from computers vents and Fans, cables etc Organize your installation disks. ...Clean up software. Clean up your operating system (OS). Upgrade and update all the software’s.Covers all the computers and the related devices in the computer lab.
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All the worn out devices should not be use againSoftware update refers to the Patching of the software that you have already installed.
Reasons for software updating
1. To ensure that a computer has the most up to date information possible2. To keep the computer running efficiently3. To put in place limitations & changes to the security of the product
Software upgrade refers to the replacement of a product with the newer version of the same product.
Risks involved in software & hardware upgrading
1. Incompatibility of new hardware / software with other pieces of hardware in the system
2. The new version may contain bugs causing the program to malfunction3. The new version may be not friendly to the user.
Importance of servicing and maintaining of computer
To prolong the life time of the computersTo pre-empt the problems that may render the proper performance of the computer system.To reduced Likelihood of Lost Files.To update outdated software programs such as application programs, antivirus, and operating system.It increases the speed performance of the computer by defragmenting hard drive, running spyware and virus removal programs as well as installing the latest drivers and software updates.It protection computers against threats by keeping spyware and anti-virus programs updated and running on a regular basis.To detect early problems and eradicate them before becoming big problemsTo keep premises, equipment, machines and the work environment safe and reliableIt helps to eliminate workplace hazards
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Tools used for computer servicing, repairing and maintenanceThese are important and essential devices that enable a person to install, remove, or perform other actions on the components within a computer. These tools/devices are categorized in the followings;
Electrostatic Discharge (ESD) ToolsHand toolsDiagnostic Tools
Software Tools Cleaning Tools Disk Management Tools Protection Software Tools
Electrostatic Discharge (ESD) Tools
These are devices used to prevent electrostatic discharge damage to computer equipment. There two types of ESD tool antistatic wrist strap and the antistatic mat. The antistatic wrist strap protects computer equipment when grounded to a computer chassis. The antistatic mat protects computer equipment by preventing static electricity from accumulating on the hardware or on the technician.
Hand tools
These are tools held in the hand and operated without electricity or other power. Most tools used in the computer assembly process are small hand tools. They are available individually or as part of a computer repair toolkit. Examples of hand tool include; Flat-head screwdriver, Phillips-head screwdriver, Torx screwdriver, Crimper, Wire cutters, tweezers, Flashlight, Wire stripper, Needle-nose pliers etc
Diagnostic tools
Diagnostic tools are tools or devices used to test, diagnose, and solve hardware-related problems. Examples of diagnostic tools include;
A digital multimeter is a device that can take many types of measurements. It tests the integrity of circuits and the quality of electricity in computer components.
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A loopback adapter, also called a loopback plug, tests the basic functionality of computer ports. The adapter is specific to the port that you want to test.
Software Tools
Like hardware tools, there are a variety of software tools that can be used to help technicians pinpoint and troubleshoot problems. Software tools helps to diagnose computer and network problems and determine which computer device is not functioning correctly. A technician must be able to use a range of software tools to diagnose problems, maintain hardware, and protect the data stored on a computer; to be able to identify which software to use in different situations.
Examples of software tools are; Disk management tools and Protection Software Tools
Disk management tools are tools that help to detect and correct disk errors, prepare a disk for data storage, and remove unwanted files.
Examples of disk management tools:
FDISK a short form for fixed disk: A command-line tool that creates and deletes partitions on a hard drive.
Disk Management Tool: used to initialize disks, creates partitions, and formats partitions.
Format: used to prepare a hard drive to store information. ScanDisk or CHKDSK: used to checks the integrity of files and folders on a
hard drive by scanning the file system, and disk surface for physical errors. Defrag: used to optimize space on a hard drive to allow faster access to
programs and data. Disk Cleanup: used to clears space on a hard drive by searching for files
that can be safely deleted. System File Checker (SFC): A command-line tool that scans the operating
system critical files and replaces files that are corrupted.
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Protection Software Tools: These are software tools used to protect data and the integrity of the operating system and hardware, guarding against virus attacks and to remove malicious programs.
Examples of protection software tools;
Windows security Center: it checks the status of essential security settings. The Action Center continuously checks to make sure that the software firewall and antivirus programs are running. It also ensures that automatic updates download and install automatically.Antivirus program: Protects computers against virus attacks.Antispyware program: Protects against software that sends information about web surfing habits to an attacker. Spyware can be installed without the knowledge or consent of the user.Window 7 Firewall: Runs continuously to protect against unauthorized communications to and from your computer.
Organizational Tools
These are tools used to keep accurate records and journals (documentation of work) during a busy workday. Example is work-order systems which are used by technicians to document their work.
Cleaning Tools These are tools used to keep the computer components and the work area clean and dust free environment.
Examples of computer cleaning tools are;
Clean cloth. Compressed Air Isopropyl Alcohol
Cotton Swabs Portable Vacuum Lens cleaning kit
N.B.The following parts and areas must be clean with the appropriate materials and detergents. Such parts include system unit, monitor, key board, mouse, component contacts, and working area must be clean.
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Preventive measure during cleaning process must be put into considerations such as;
Proper handling of the computer parts not to fall down Ensuring that the appropriate tools are use and they must be in good
conditions. Before cleaning, ensure that those parts such as monitor, key board are
plug out of power. After cleaning them, plug back the power cord safely. Do not use a vacuum cleaner inside a computer or on a laptop keyboard
because the plastic parts of the vacuum cleaner build static electricity. Use little amount of water so that it does not drop inside the monitor
Keyboard Navigation and the Mouse
The keyboard
A keyboard is a primary input device made up of keys with numbers, letters, symbols and special
keys used to enter data into the computer.Each press of a key corresponds to a single written
character of text, but to produce some symbols, it requires pressing and holding several keys
simultaneously.
A keyboard is the main and most reliable computer input device which was invented by
Christopher Latham Sholes who was an American newspaper publisher .In 1866; he invented the
first practical typewriter and the QWERTY keyboard still in use today.
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Keyboard layouts
The arrangement of the English language keyboard keys was modeled after the QWERTY type
writer keyboard developed by Christopher Sholes in 1868.
Its name was derived from the first six letters at the top of the keyboard.
NB; The alternative to the QWERTY keyboard is the Dvorak keyboard developed by Dr.
Dvorak in 1936. With the Dvorak, the most used letters are positioned in the middle row of the
keyboard, intending to reduce typing time and finger movements.
Types of keyboards
A standard computer keyboard
Wireless keyboard
Handheld keyboard
Laptop keyboard
Ergonomic keyboard
Enhanced keyboard
Parts of a computer keyboard
Functional keys
These are keys found across the top row of the keyboard. Each key is composed of letter F and a
number ranging from 1 to 12.
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Each functional key performs a specific operation based upon the software being used.
Numeric keypad
This is an extra section to the right of the keyboard.
Navigation/Cursor/Arrow keys
These keys are used to navigate through documents and websites. They include the up, down,
left, and the right arrows.
Typewriter Keypad (Alphanumeric Keypad)
This consists of the keys in the centre of the keyboard. It has buttons with alphabetical letters and
numbers hence the name alphanumeric keypad. Most of the typing is done with these keys.
Special Keys
These are the keys that are used to perform specific functions in the computer. They include;
Shift key, Tab key, Control key, Caps Lock, Num Lock, Backspace key, Enter key, Delete key,
Alt key, etc.
Functions of some selected keys on the keyboard
i. Backspace key
It deletes the characters to the left of the cursor and moves the cursor to that position. Ctrl+
Backspace key removes the whole word to the left of the cursor.
ii. Caps Lock Key
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A toggle key that, when activated, causes all alphabetic characters to be uppercase. To facilitate
continuous typing in upper case when activated.
iii. Delete Key
To remove the character, space, text or word to the right of the cursor position
Ctrl+Del remove the whole word to the right of the cursor position.
Sometimes labeled Del, deletes the character at the current cursor position, or the selected object,
but does not move the cursor.
For graphics-based applications, the Delete key deletes the characters to the right of the insertion
point.
iv. Space bar
To create space
For alignment
Moving the cursor to the next line
Pausing music in some music programmes e.g. Power DVD,
Playing games e.g. in pinball
Resizing or closing the current window with a modifier key e.g. Ctrl Key +Spacebar
Helps in scrolling in some web browsers when used with Shift Key
v. Shift Key
Activates second function of different keys
Activates sticky keys
Selects files and folders in specific order
Modifies function Keys e.g. Shift + F1 = F13 and Shift +F2=F14.
Anchors the insertion pointer in word processors
Used in modifying the mouse behavior while using a web browser
vi. Ctrl key
Short for Control, this key is used in conjunction with other keys to produce control characters.
The meaning of each control character depends on which program is running.
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vii. Enter Key
Used to enter commands or to move the cursor to the beginning of the next line
viii. Esc Key
Short for Escape, this key is used to send special codes to devices and to exit (or escape) from
programs and tasks.
ix. Alt key
Short for Alternate, this key is like a second control key.
x. Arrow Keys
Most keyboards have four arrow keys that enable you to move the cursor (or insertion point) up,
down, right, or left. Used in conjunction with the Shift or Alt keys, the arrow keys can move the
cursor more than one position at a time, but this depends on which program is running.
Advantages of using a computer keyboard
1. Keyboards are very common (commonly supplied with computers)
2. Entering data and commands with keyboard is faster as compared to the mouse
3. Keyboards are more reliable
4. They are used for computer gaming
5. A keyboard is used to control computer
Disadvantages of using computer keyboard
1. It takes a lot of time to practice in order to type quickly
2. Keys can easily become faulty due to dust.
3. Some keyboards keys are very hard to press, causing fingers to hurt.
Computer key board combination and their uses
Alt+Tab: Switch between open programs or windows
Ctrl+A: Select all items in a document or window
Alt+F4: Close the active item, or exit the active program
Ctrl+S: Save the current file or document.
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Ctrl+C: Copy the selected item
Ctrl+X: Cut the selected item
Ctrl+V: Paste the selected item
Ctrl+Z: Undo an action
F1: Get help
F2: Rename a selected item.
Tips for using your keyboard safely
Using keyboard improperly can cause soreness or injury to your wrists, hands, and arms,
particularly if you use your computer for long periods of time. To avoid this:
Place your keyboard at elbow level. Your upper arms should be relaxed at your sides.
Center your keyboard in front of you. If your keyboard has a numeric keypad, you can
use the spacebar as the centering point.
Type with your hands and wrists floating above the keyboard, so that you can use your
whole arm to reach for distant keys instead of stretching your fingers.
Avoid resting your palms or wrists on any type of surface while typing. If your keyboard
has a palm rest, use it only during breaks from typing.
While typing, use a light touch and keep your wrists straight.
When you're not typing, relax your arms and hands.
Take short breaks from computer use every 15 to 20 minutes.
The computer mouse
A mouse is a handheld operated input device used to position the cursor, point, select and move
objects on the computer screen.
Wheel Mouse housing
Secondary/Right mouse button
Connecting cable Primary/Left mouse button
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The top and sides of a mouse have one to four buttons; some also have a small wheel. The
bottom of a mouse is flat and contains a mechanism, such as a ball or a light that detects
movement of the mouse.
TYPES OF MICE
1. Mechanical mouse
A mechanical mouse has a rubber or metal ball on its underside. Electronic circuits in the mouse
translate the movement of the mouse into signals the computer can process.
2. Optical mouse
Most computer users today have some type of optical mouse, which has no moving mechanical
parts inside. Instead, an optical mouse uses devices that emit and sense light to detect the mouse's
movement.
Some use optical sensors, and others use a laser. An optical mouse is more precise than a
mechanical mouse and does not require cleaning as does a mechanical mouse, but is more
expensive.
3. Air mouse
Is a motion-sensing mouse that, in addition to the typical buttons, allows you to control objects,
media players, and slide shows by moving the mouse in predetermined directions through the air.
For example, raising the mouse up would increase the volume on your media player.
4. Cordless mouse
The cordless mouse is a lot better than a normal mouse. It reduces the amount of work space
needed to move the mouse around.
This mouse runs on a battery. When you move the mouse it sends an infrared beam to a sensor
which interprets it causing the pointer to move
Mechanical mouse Optical mouse
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Air mouse Cordless mouse
Basic activities performed by a mouse piece
1. Point
Means positioning the pointer on the screen to an object such as a button, a menu, an icon, a link,
or text
2. Click
Means pressing and releasing the primary mouse button, which selects or deselects items on the
screen or starts a program or program feature.
3. Right-click
Involves pressing and releasing the secondary mouse button, which displays a shortcut menu
4. Double-click
Means pressing and releasing quickly the primary mouse button twice without moving the
mouse; this action starts a program or program feature.
5. Drag
Means pointing to an item, holding down the primary mouse button, moving the item to the
desired location on the screen and then releasing the mouse button
6. Right-drag
Displays a shortcut menu after moving an object from one location to another
7. Rotate wheel (Scrolling)
Involves rolling the wheel forward or backward that scrolls up or down a few lines
Advantages of using a computer mouse
It is user friendly
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It is faster to select items
It is easy and convenient to use with graphical user interface
It is good for limited desk space
Disadvantages of using a computer mouse
Difficult to input ex using a mouse
A mouse in not accurate enough for drawings
It is very slow to issue command using a mouse
The computer system Unit
The system unit is a box-like case that houses the electronic components such as the
motherboard, the disks, processor, memory, drive bays, the power supply and cooling systems
and other electronic components of the computer that are used to process data. All other
computer system devices, such as the monitor, keyboard, and mouse, are linked either directly or
indirectly into the system unit.
A drive bay is a rectangular opening inside the system unit that typically holds disk drives.
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The computer system unit provides the following functions
1. It contains the framework to support a computer’s internal components and provide an
enclosure for added protection.
2. They provide an environment designed to keep the internal components cool.
A system unit contains the following electronic components;
Power Supply,
Mother board,
CPU,
System Clock,
Ports and connections
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Internal cables
Storage drives (HDD,FDD,ODD)
RAM chips, Expansions lots,
Bus lines,
Ports,
PC slots and Cards,
Peripheral
The motherboard
The mother board is a single circuit board that provides the path through which the processor
communicates with memory components, other components, and peripheral devices.
It is the main circuit board in the system unit. It houses the CPU chip, Main memory chips and
expansion slots into which other circuit board can be inserted for the expansion of the computer
system.
Basic parts of a computer motherboard
An expansion slot is a socket on the motherboard that can hold an adapter card. An adapter card,
also called expansion card, is a circuit board that increases the capabilities of the system or
provides connections to peripherals. Some motherboards include all necessary capabilities and
do not require adapter cards.
Adapter cards are used for many supplemental capabilities, such as more memory, higher-
quality sound devices, a modem, extra ports, or graphics capabilities.
Commonly used adapter cards and their functions
Adapter Card Purpose
Sound card Connects speakers or a microphone
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MIDI card Connects musical instruments
Network interface card
(NIC)
Connects other computers
Video card Connects a monitor
USB card Connects USB devices
TV tuner card Allows viewing of television channels
Video capture card Connects a video camera
Modem card Converts telephone or cable analog signals to digital and vice
versa
FireWire card Connects FireWire devices
N.B.Plug and Play (pnp) is the ability of the computer to recognize a new device and assists
in the installation of the device by down loading the necessary drivers automatically and
checking for conflicts with other devices.
It refers to the computer’s capability to automatically configure adapter cards and other
peripherals as you install them when the computer is still running.
Buses
The bus is a common electrical path that enables data flow between the various system
components. A bus allows the various devices inside and attached to the system unit to
communicate with each other.
Buses are used to transfer bits;
From input devices to memory,
From memory to the CPU,
From the CPU to memory,
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From memory to output or storage devices
All buses consist of three parts:
1. A control bus is part of the system bus, used
by CPUs for communicating with other devices within the computer. A control bus
carries commands from the CPU and returns status signals from the devices.
2. Address bus carries the information about the device with which the CPU is
communicating
3. Data bus carries the actual data being processed,
Types of buses
1. System bus which is part of the mother board and connects the CPU to main memory.
2. Expansion bus which allows the CPU to communicate with peripheral devices
Examples of expansion buses and their functions
Bus Function
ISA (Industry Standard Architecture) bus It connects devices such as modem & sound cards, mouse
PCI (Peripheral Component Interconnect) bus To connect sound and network cards to the motherboard
PCI Express (PCIs) bus To connect a computer to one or more peripheral devices.
The Accelerated Graphics Port (AGP) bus It enable 3-D graphics to display quickly on ordinary
personal computers
Universal Serial Bus (USB) To define cables, connectors and protocols for connection,
communication, and power supply between personal
computers and their peripheral devices.
Fire Wire bus It is used to connect multiple devices to a computer to
enable high-speed transfers between computers.
PC Card bus It expands the bus bandwidthand throughput to 32 bits at
33MHz
Ports
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A port is a socket on the outside of the system unit that is connected to an expansion board on the
inside of the system unit. It is the interface or point of attachment to the system unit. Peripheral
devices, such as;
A keyboard, monitor, printer, mouse, digital camera, microphone, etc. often attaches by a cable
to a port on the system unit. Most of the time, ports are located on the back of the system unit,
but they also can be placed on the front.
Types of ports
Port Purpose
Serial port It is used to connect serial devices to the computer
and capable of transmitting one bit at a time.
Parallel port Parallel port is a parallel interface used for
connecting external devicesuch as a printers.
USB (Universal Serial Bus) port USB ports allow USB devices to be connected to
each other with and transfer digital data
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over USB cables.
Fire Wire port (IEEE 1394port) Is a port that provides a high-speed connection
between a computer and peripheral devices
MIDI (Musical Instrument Digital Interface) port Is an electronic connector that connect a wide
variety of electronic musical instruments, computers,
and related music and audio devices
eSATA (external Serial Advanced Technology
Attachment) port
Is a connector accessible from outside the computer,
to provide a signal (but not power) connection for
external storage device
PCMCIA (Personal Computer Memory Card
International Association) port.It is a configuration port used for computer parallel
communication peripheral interface, designed
for laptop computers.
SCSI (Small Computer System Interface) ports A SCSI connector is used to connect computer parts
that use a system called SCSI to communicate with
each other
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IrDA (Infrared Data Association) port It is a port that allows the user to transfer data from
one device to another without any cables.
Bluetooth port A Bluetooth port enables connections for Bluetooth-
enabled devices for synchronizing. There are two
types of ports: incoming and outgoing. The incoming
port enables the device to receive connections from
Bluetooth devices while the outgoing port makes
connections to Bluetooth devices.
VGA (Video Graphics Adapter) port VGA) connector is a three-row 15-pin DE-
15 connector used to connect an analog PC monitor
to a PC or laptop
Ps/2 port The PS/2 port is a 6-pin mini-DIN connector used for
connecting keyboards and mice to a PC compatible
computer system
Network Port A network port is an endpoint of communication in
an operating system, which identifies a
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specific process or a type of network service running
on that system
Audio port Audio port is used to link the computer's sound
hardware with speakers, microphone, headsets or
other audio equipments.
NB: Hot plugging / hot Swapping; is the ability to add or remove devices while a computer is
running.
Power supply unit
It provides the necessary electrical power to make the PC operate. The power supply converts
alternating current (AC) power from the wall outlet into direct current (DC) power which is a
lower voltage.
Memory chips (RAM& ROM)
These are devices that provides vast amount of memory required by the computer. Read Only
Memory (ROM) chips are located on the mother board. They contain instructions that the CPU
can access directly. ROM chips stores basic instructions for booting the computer and loading
the operating system.
Random Access Memory (RAM) is the temporary storage for data and programs that are being
accessed by the CPU.
Cooling systems (fans)
Case fans are devices installed inside the system unit to make the cooling process more efficient.
A heat sink draws heat away from the core of the CPU. A fan at top of the heat sink moves heat
away from the CPU. Cooling a system is necessary to protect the internal components from
damaged and also to fasten the working of the computer system.
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Internal cables
Hardware inside the system unit connects to the mother board by use of internal cables.
The computer clock
Every computer contains two types of clocks; Hardware clock (Real-time clock, RTC), and
System clock / Virtual Clock
Hardware Clock
It is a clock that maintains the time and date.
It is from this clock that the system clock is set when a computer is switched-on.
It runs continuously whether the computer is on or off.
It is maintained by use of a CMOS (Complementary Metal Oxide Semi-conductor)
battery.
System Clock
The system clock is a small crystal chip that is used by the CPU to synchronize the timing of all
computer operations. The faster the clock, the more instructions the CPU can execute per second.
The speed at which a processor executes instructions is called clock speed which is measured by
the number of ticks per second.
Peripheral Devices;
Peripherals are the generic name given to all input, output, and secondary that are part of a
computer system. These are any external devices that attach to the system unit. They include
keyboard, mouse, printers, scanners etc.
Central processing unit (CPU)
Central processing unit is an electronic device that interprets and carries out the basic
instructions that tell the computer how to work. It is the “Brain” of the computer.
Categories of computers
Computers are categorized according to how the processed data is
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represented.
Therefore they are categorized into three categories i.e.
(a) Analog Computers
(b) Digital Computers
(c) Hybrid Computers
Analog Computers
Analog computers are computers used to process data in a continuous form. These
computers operate by measuring rather than counting.
These computers employ physical variables like temperature, voltage, weight, pressure,
speed to represent the quantities being manipulated.
Analog computers are used in engineering and scientific applications, weather
forecasting, green house controls and in manufacturing industries.
Analog data is data that is continuous in nature such as temperature, voltage, pressure
& weight
Examples of analog computers include; Thermometers, Voltmeters, Tide
predictors, Speedometers etc
Digital Computers
These are computers that process data in discrete form or value. Discrete values are
numbers that can be defined like, 1, 2, 3, etc.
They can count and process data in a more accurate way. They convert data into
digits) binary digits of 0 &1). These are computers used for business and scientific
applications.
Digital data is data that is discrete in nature such as 0 and 1.
Examples of digital computers include; Digital Watches, personal
computers, mobile phones.
Advantages of digital data over analog data
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Digital data is more accurate that analog data
Digital data occupies less storage space than analog data
Digital data is transmitted faster than analog data
Digital data produces clearer output that analog data
Hybrid Computers
These are computers that have the combined features of both the digital and
analog computers.
Hybrid computers measure physical quantities and represent it values in a digital form.
The analog computer takes measurements in a continuous form and converts it into
numbers and supplied to digital components in the system.
Examples of hybrid computers include; digital petrol pumps, computer devices used in
hospitals to measure parameters such as patients temperature, blood pressure etc.
Differences between Digital and Analog
Digital Analog
More Accurate. Less accurate compared to digital.
Use binary code to represent information. Use a changing phenomenon due to environment
Have no interference and background noise. Have interference and background noise.Generally fast and cheap. Generally slow.Data does not degrade over time during transmission.
Data degrades over time during transmission.
Data can be compressed. Data can’t be compressed.Classification of computers
Computers are classified according to the following functionalities;
Purpose/Function
Size
Processor power
Classification of computers by Purpose
These are computer classified according to the work they are designed for, and they are further
classified into two classes;
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Special Purpose Computers
These are computers that are designed to handle only one particular task. Their form of operation
is limited in nature.
Currently, these computers are employed in devices like missiles. These will never do anything
like word processing.
Examples of special computers include; Digital watches, Pocket calculators, Lifts in
buildings, Missiles
General Purpose Computers
These are computers designed to carry out a wide variety of tasks.
Among the variety of tasks perform by general purpose computers include performing
calculations, keep date and time, process word documents, store databases, tabulate
student‘s grades, play games, etc.
Examples of general purpose computers include;
Stand alone computers
Stand alone computers are computers that are not connected to a network and is capable of
performing the operations in the information processing cycle.
Networked computers (NC);
These are computers designed specifically to connect to a network especially the internet.
Real time systems
These are systems that process data without significant delay such
as;
Anti – missile defense systems,
Airplane landing control systems
Flight simulation systems
Electronic fund transfer systems
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Ticket reservation systems.
Classification of computers by size
According to size or capacity, we base on the physical size the number of people the computers
can accommodate at the same time. Digital computers can be grouped into four classes as
follows:
.
Super Computers
Characteristics of super computers
They have a very high processing speed
They have a very high storage capacity
They are the biggest types of computers
They are very expensive computer
They are the most powerful computers
They are used for complex and sophisticated mathematical calculations
Examples of Super Computers: Cyber 70, IBM 4381 etc.
Mainframe Computers
These are powerful computers used mainly by large organizations for bulk data processing such
as census, and financial transaction processing.
They are very large and expensive computers capable of supporting hundreds of users
simultaneously.
These computers are designed to handle huge volumes of data and information.
Characteristics of mainframe computers
They can accommodate many users at a time.
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They have a high storage capacity
They are bigger than mini computers
They have a high processing speed
They support a wide range of peripheral devices
They are sensitive to changes in temperature such as humidity; dust hence should be kept
in a well air conditioned room
Examples of Mainframe Computers; ICL 39 series, and CDC Cyber series
Mini Computers
Mini computers are multi-user computers that lie in the middle range between mainframe
computers and the smallest single-user systems.
They are similar to main frames but they are smaller in size, support a limited number of
peripheral devices connected to them.
They have a lower speed, have lesser storage capacity, and support fewer numbers of users at the
same time than compared to main frames
They can be used for applications such as accounts, payroll, stock control, etc.
They are used in industries to control the manufacturing process e.g. Car
assemblies, UNEB, UEB, etc.
Characteristics of mini computers
They are smaller in size that mainframe computers
They support limited peripheral devices
They have lower storage capacity
They have a very low processing speed
They support limited number of users between 50-200
Examples of minicomputer include; PDRS, PDP-11, IBM AS400 range, VAX. etc.
Micro Computers /Personal Computers (PCs)
Microcomputers are computers that can perform its entire input, process, output and storage
activities y itself.
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Microcomputers are smaller than mini computers and are a single user capacity.
The keyboard, system unit and monitor of a micro computer can be used by one person at a time.
They are mostly used computers in day-to-day work.
Characteristics of Micro computers
They have smaller memory capacity
They use large scale interpreted circuits
They are relatively cheap, portable and convenient
They are smaller than any other computers
They are single user computers with network technology
They support wide few peripheral devices
They have high processing speed
They are computers with a micro processor as its central processing unit
Examples of micro computers include;
Desktop Computers
These are microcomputers designed to be stationed in one place preferably on top of the desk.
They can be used in offices, computer labs. They are the standard computers.
Tower Model Computers
These computers have a tall and narrow system unit that usually sits on the floor.
Laptop Computers
These are portable personal computers which is small enough to fit on the lap such that even if
one is in a bus or plane can still work like one on a desk top.
Notebook Computer;
This looks like a laptop but it is much smaller than a laptop.
Palmtop Computers / Personal Digital Assistants (PDAs)
These are hand held computers used by people who are ever on move by carrying it in the
palms.
Classification of computers by processor power
Micro Computers can be classified by their microprocessor model name or model number.
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The leading processor chip manufacturers for personal computers are Intel, AMD, IBM, and
Motorola.
Due to the rapid changes in technology processor power is also rapidly increasing. Computers
are getting faster and faster each time a new microprocessor chip is introduced.
Examples of Microprocessors
The most common types of processor power are:-
80286,
80386,
Pentium I,
Pentium II,
Pentium III,
Pentium IV,
Pentium Duo core,
Core 2 Quad,
Celeron,
Celeron D,
Xeon,
Opteron,
Athlon,
Itanium
Intel Dual Core
Intel Dual core i3
Intel Dual core i5
Intel Dual core i7 etc.
The unit for measuring the processing power is the Hertz.
Due to the rapid changes in technology, processor power is also rapidly increasing.
Computers are getting faster and faster each year. The higher the processing powers the
faster the computer. Earlier computers had processing power of less than 0.4MIPS but today
15 MIPS is the least. (MIPS: Millions of Instructions per Second).
Computer information system
A computer system is a functional unit consisting of integrated assembly of devices, centered
on at least one processing mechanism which are used to input, process, store, and output data
and information. A computer system consists of interrelated organs or parts which function
together for the same goal. Failure of one of the system components may imply failure for the
whole system.
Components of a computer information system;
Hardware
Software
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Data
Information
Users (Human ware)
Procedures
Communication
Hardware
Hardware comprises of the electronic and the electromechanical parts of the computer.
Hardware devices are the physical and tangible of a computer. Examples include;
Input devices
Processing devices
Storage devices
Output devices
Communication devices
Software
Software is electronic instructions that tell the computer how to perform a task. These are a
series of programs (instructions) that tell the computer what and how to work.
Data
Data refers to raw facts and figures that are processed into information. Data is the foundation
for information
Information
Information is the processed data which is organized, meaningful and useful.
Importance of information
In all organizations, managers depend on information to make decisions.
They also base on information when planning for the organizations.
They base on information when analyzing their performance.
They depend on information to forecast the likely outcomes of certain actions.
Information helps in discovering the past, present and future.
Procedures
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These are rules or guidelines for people to follow when using hardware, software, and data. They
normally appear in documentation materials which contain guides for using the hardware and
software.
Users (human ware)
Human ware refers to the people who operate and initialize instructions to the computer system.
It is the most important component of a computer system
They design and develop computer systems, operate the computer hardware, create the
software, and establish procedures for carrying out tasks.
There are two categories of computer users;
Ordinary users are people without much technical knowledge of computers but uses computers
to produce information for professional or personal tasks, enhance learning, or have fun.
Professional users are people who had formal education in the technical aspects of
computers such as;
Computer programmer
System analyst
System administrator
Database administrator
Network administrator
Importance of users
Data entry
Manipulating the computer
system
Programming the computer
Administering the network
Analyzing the computer
system, etc.
Communication
Communication refers to the process of transferring data and information from one place to
another digitally.
Computer communication allows sharing of hardware, software and transfer of data and
information stored among computers in a network like Internet. It also facilitate communications
between people e.g. through e-mail. Examples include; Cables, Switches, Routers Modems, etc
Importance of communications
Linking up computer devices and computers
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Enabling the flow of data
Enabling the flow of information
Enabling the flow of instructions
Networking of computers
Data and Information
Data
Data refers to raw facts and figures that are processed into information. Data is the foundation
for information. Data is classified into two categories that input data and output. Examples of
data include;
letters (e.g., a, b, c, ...)words and symbolsNumbersexamination scoresmusical notesNames e.g. Moses
Information
Information is the processed data which is organized, meaningful and useful. Is manipulated/
processed data, examples include,
Words (e.g., apple, boy, cat)a report, a letter, an essaya mathematical formulacomments, gradesa piece of music, a song
Information processing Cycle
This is a series of activities that take place in transforming data into information. It involves
input, processing, output and storage of information.
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The four basic stages of information processing cycle include;-
Input of data
This is a means by which data is entered into the processing system by the use of the keyboard,
mouse, touch pad, microphone, scanner etc. It involves collecting of data from their sources and
recording it onto some media such as paper, questioners, voice or video recording and preparing
of the collected data by copying, grouping, or arranging of data in a more convenient way for
input.
Storage of data and information
This process includes storing of data and information. When data in entered, it is stored
temporarily by RAM to be process by CPU and when the process of execution is done, the
processed data is stored in storage devices such as floppy disks, flash disk, flash memory, disc
drives, and hard drives etc which are later retrieved for use references.
Processing of data
This involves the manipulation or arithmetic & logical operations of the input data. The
processing stage is based on the user’s instructions. The central processing Unit (CPU) is the one
responsible for processing of data.
Output of information
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DATA
PROCESSING OF DATA BY
CPU
MEMORY
Storage Area (RAM & ROM)
INFORMATIONOUTPUTTT
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Output is a means processed data is obtained and can be viewed in a readable form example as a
report. Devices commonly used by which for output of data include monitor screen, printer,
speakers etc.
Notice: In summary, there are four major functions of a computer:
1. Accepting data
2. Storage of data and information
3. Processing of data
4. Producing output
Advantages of using computer systems for information processing
1. Enormous amounts of data can be stored permanently for future use.
2. Computers can process large amount of data and generate error free results provided the
data entered is correct.
3. Large numbers of tasks can be performed at very fast processing speed.
4. The degree of accuracy is very high.
5. Efficiency and productivity in information processing can be realized.
6. The operations like deletion and modification of data can be done very easily.
7. Tasks can be completed with minimal human intervention
8. It allows for the decisions and logical comparisons.
9. It allows for the creation of standard libraries.
10. Sharing of data and information is possible when the computers have communication
capabilities.
11. It is possible to obtain the results in the formatted form.
12. The management can observe information and trends more quickly.
Disadvantages of using computer for information processing
1. The initial investment costs are high, such as costs on computers, skilled labor force and
software.
2. Mechanical faults within the computer system or damage may lead to system failure.
3. Extra costs are required to employ specialized staff or personnel to operate the computers
and even design the data processing system.
4. Face to face interaction among the staff may be reduced.
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5. There is easier transmission of malicious codes or viruses in a network environment.
6. Some jobs may be lost due to computerization and thus may render the morale of the
workers.
7. The networking environment is susceptible to human abuse.
8. Extra costs may be needed in the security to protect personnel and staff from preying
eyes such as the use of sensor, CCTV cameras.
TOPIC 2:
COMPUTER HARDWARE
Introduction to Computer Hardware
Computer hardware refers to the physical and tangible components of a computer. These are
devices you can see, touch and feel.
Categories of Computer hardwires
1) Input hardware
2) Storage hardware
3) Processing hardware
4) Output hardware
5) Communication (Networking) hardware
Input hardware
Input is any data or program instructions people enter into the memory of a computer.
Terms related to input
Data
This is collection of raw unorganized facts, and figures to be processed by a computer.
Information
Information is processed data that is organized, meaningful and useful.
A program
Is a series of instructions that directs a computer how to perform the tasks necessary to process
data into information; A program is written by a programmer and then store the program in a
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file that a user can execute (run).
A command
Is an instruction given to a computer program to perform a specific action; Commands can be
issued by typing keywords, pressing special keys on the keyboard, selecting menu choices,
clicking the mouse on a graphical user interface, speaking into a microphone, or touching an area
on a screen.
A user response
Is an instruction users issue to the computer by replying to a question posed by a computer
program; A response to the question instructs the program to perform certain actions.
Input devices
These are hardware components or devices that allow the user to enter data and instructions
(programs, commands, and user responses) into the computer. Input devices translate data
and communications into a form that the computer can understand. Each input device
outputs data in a unique way depending on the type of data being input. The data may be in
form of a sound, characters, graphics etc.
Examples of input devices
Keyboard
Pointing devices
Controllers for Gaming and Media
Players
Audio Input devices
Video Input devices
Scanning devices
Reading devices
Terminals devices
Biometric Input devices
Remote control
Sensor and Remote sensor
Keyboard
A keyboard is a primary input device made up of keys with numbers; letters, symbols and
special keys used to enter data into the computer by pressing of a key corresponds to a
single written character of text.
Pointing devices
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Pointing devices are input devices that allow you to control a pointer on the screen and interact
with computer via a graphical user interface (GUI). Examples of pointing devices include;
A Mouse
A
trackball
A touch
pad
Pointing Stick
A touch screen
A light pen
A stylus and graphics tablet
Digitizers
A Mouse
This is a hand operated device used to position the cursor, point, select and
move objects on the computer screen.
A trackball
A trackball is like an upside-down mouse. It is a stationary pointing device with a ball
mechanism on its top. It is operated by rolling the ball directly with your hand.
A touch pad
A touchpad is a small, flat, rectangular pointing device that is sensitive to pressure and motion
used to move the pointer by sliding your finger tip across the surface of the pad.
Pointing Stick
A pointing stick is a pressure-sensitive pointing device shaped like a pencil eraser used
to move the pointer by pushing the pointing stick in any direction with your finger.
A touch screen
A touch screen is a touch-sensitive input display device used by touching any items, icons,
words, pictures, numbers, letter, or locations identified on the screen.
A light pen
A light pen is a handheld input device that detects the presence of light by pressing
the light pen against the surface of the monitor screen, a special type of paper, or a
graphic tablet. It can be used for writing, drawing by taping on the flat surface
drawing by taping on the flat surface.
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A stylus and graphics tablet
A stylus is a small metal or plastic device that looks like a tiny ink pen but uses
pressure instead of ink to write text and draw lines on a pressure sensitive screen.
Stylus pen is a pen that allows the user to draw on a digitizing tablet that mirrors the
surface area of the computer screen.
A graphics tablet is a flat, rectangular, electronic plastic board on which a stylus writes or draws
Digitizers
These are devices that look like a mouse, except that it has a glass with a cross hair in the middle.
It is used with a digitizing tablet in making maps (cartography) and architectural drawings to
accurately trace out lines on a map. They are commonly used by architects, mapmakers,
designers, artists, and home users create drawings and sketches by using a pressure-sensitive pen
or a cursor (digitizer) on a graphics tablet. A cursor looks similar to a mouse, except it has a
window with cross hairs, so that the user can see through to the tablet
A mouse
A trackball A touch pad Pointing stick
A touch screen A light pen Graphic tablet Digitizer
Controllers for Gaming and Media PlayersThese are input devices used in video games and computer games to direct
movements and actions on- screen objects. Examples of game controllers and
media players include;
Game pads,
Joysticks and wheels,
Light guns,
Dance pads
Touch sensitive pads
A game pad
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A game pad is an input device that is used to control the movement and actions of players
and objects in video/computer games by pressing its buttons with thumbs and moving sticks
in various directions to trigger events.
Joystick and wheels
A joystick is a handheld vertical lever mounted input device with buttons called triggers used by
moving the lever in different directions to control the actions of the simulated vehicle or player
by pressing the triggers to initiate certain events.
A wheel is a steering wheel- type input device used by turning the wheel to simulate driving a
vehicle. Most wheels also include foot pedals for acceleration and braking actions.
A light gun
A light gun is one the input devices used to shoot targets and moving objects by pulling the
trigger on the weapon or an item on the computer screen.
A dance pad
A dance pad is a flat electronic input device divided into panels that users press with their feet
in response to instructions from a music video game. It is operated by stepping on the correct
panel at the correct time, following a pattern that is synchronized with the rhythm or beat of a
song.
The touch-sensitive pad
It is an input device contains buttons that are operated with a finger by scrolling through when
playing music, viewing pictures, watching videos or movies, adjusting volume, and customizing
settings.
A game pad Joystick A wheel
A light gun A dance pad
Audio input
Audio input is the process of entering any sound into the computer such as speech, music, and
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sound effects. To enter high-quality sound into a personal computer, the computer must have a
sound card.
A sound card is a device that can be slotted into a computer to allow the use of audio
components for multimedia applications. Without a sound card, audio input and output is not
possible.
Examples of audio input devices include;
Microphones
Voice recognition equipment
Tape players,
CD/DVD players,
MIDI devices
Dictaphone etc
A microphone
A microphone is an audio input instrument used for converting sound waves into electrical
energy variations, which may then input into the computer for processing, recording or audio
playback.
Microphones are connected to the sound card in the system unit.
Voice recognition equipments (VRE)
These are audio input devices used to capture sound such as multimedia computers, tape
recorders etc .they are capable of distinguishing spoken words and then converts them into text.
Tape players
Tape player is an analog audio device that records and plays back sounds, including articulated
voices, usually using magnetic tape in a cassette, for storage.
MIDI (Musical Instrument Digital Interface)
MIDI (musical instrument digital interface) is the standard that defines how digital musical
devices represent sound electronically. MIDI devices such as electronic pianos allow users to
record and edit music to produce sound.
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Dictaphones
Dictaphone is an electronic audio input device that allows the user to record or create spoken
words or voices that are later repeated them aloud so that they can be written down as important
notes.
Microphone CD/DVD player Voice recognition equipment
Tape player MIDI Dictaphones
Video input
Video input is the process of capturing full-motion images such as still photos, motion pictures,
graphics, and video and storing them on a computer‘s storage medium.
Video input devices are input devices used to capture and enter images such as still photos,
motion pictures, graphics, video etc. into the computer for processing.
NOTICE; To enter video from an analog device into a personal computer, the analog signal
must be converted to a digital signal by plugging a video camera or other analog video device in
a video capture port on the system unit.
Common video input devices include:
Digital camera
Digital video camera
A webcam
Film camera
Camcorder
Digital camera
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A digital camera video input device that allows users to take pictures and store the photographed
images digitally instead of storing on a traditional film. When you take pictures, the images are
electronically stored in the camera.
Types of digital cameras
Studio cameras, Field cameras
Point-and-shoot cameras
A studio camera is a stationary camera used in professional studio work. It is the most expensive
and has the highest quality.
A field camera is a portable camera that has many lenses and other attachments. It often used by
photo journalists.
A point-and-shoot camera it is more affordable, lightweight and provides acceptable quality
photographic images for home or small business users. A point-and-shoot camera often has
features of flash, zoom, automatic focus, and special effects. Some allow users to record short
audio narrations for photographed images, record short video clips, etc.
Digital video camera
A digital video (DV) camera is an input device by contrast records video as digital signals
instead of analog signals. For a video or the image to be displayed, it requires a video capture
card to convert analogue video signals into digital signals so that the computer can understand
the images
A webcam
A Web cam, also called a PC video digital camera is a type of digital video camera that
usually sits on top of the monitor that allows users to record, edit, capture video and still
images, and make video telephone calls on the Internet. During a video telephone call, both
parties can see each other as they talk. Some laptop computers have built-in Web cams.
Webcams enable users to:
capture video and still images,
send e-mail messages with video attachments,
add live images to instant messages,
broadcast live images over the Internet,
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and make video telephone calls
Camcorder
This is a light weight video camera that records data in digital form onto a storage device such as
a video tape.
Film cameras
Film cameras are cameras that expose photographic film to light in order to take a picture. A
film is a chemical emulsion on a plastic substrate that is sensitive to light. When exposed, an
analogous image of the scene is created within the chemical layer of the material; thus, film
cameras are analog cameras.
Digital Camera Digital video camera
Webcam Camcorder Film Camera
Advantages of a digital Camera over the ordinary film camera
They are environmental-friendly
They records massive amount of videos unlike film camera
They have user-friendly features
They store large amount of Photos
They have high Operating Speed compare to film camera
They save money for buying films.
They allow images taken to be previewed and even edited on the camera.
Unwanted images can be deleted after preview.
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Digital cameras are best for three – dimensional objects unlike film cameras
Disadvantages of digital camera
Digital cameras are very complex because the user must know how to upload and edit
photos using a computer
Digital cameras are sensitive and susceptible to extreme conditions such as heat, extreme
cold and moisture in comparison to the old film cameras that causes their malfunctions
Digital cameras consumption power faster than film cameras. This makes it necessary to
keep a few spare batteries in hand, especially during lengthy photo sessions.
They are normally expensive than the ordinary film cameras with the same functions.
Photo printing costs are higher than that of the ordinary film cameras.
Scanning devices
These are devices that capture data directly from source documents and converts it into a digital
form that can be stored into a computer. Most of the scanning services is done by a scanner
especially optical scanners.
A scanner is a light-sensing input device that converts hardcopy documents, drawings, or
pictures to an electronic version (softcopy), which can then be stored on a disk. The electronic
version of scanned material is in the form of rows and columns of dots called a bitmap. Each dot
on a bitmap consists of one or more bits of data.
N.B. Bitmap display screen permits the computer to manipulate pixels on the screen individually
rather than, enabling software to create a greater variety of images.
Optical Scanners
Optical scanners are light-sensing input devices that can convert text, drawings, or pictures
into computer-recognizable digital data by using a form of optical recognition. In a process
called imaging, a scanner converts source documents to an electronic version, which can then
be stored on a disk and retrieved when needed.
Examples of optical scanner include
Flatbed scanner
Sheet-feed scanner
Drum scanner
Handheld scanner
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NB: The quality of a scanner is determined by its resolution and color depth.
Advantages of scanners
Scanners provide high quality in terms of resolution for both color and black and white
documents. They also provide enough detail and resolution to handle images,
photographs, graphics and designs.
Scanners make it unnecessary to retype text or redraw images. Thus, you can reproduce a
document or picture in as little as 10 seconds, even if the original took hours or days to
produce. The scanner can make this copy without damaging the original item.
Scanners don't depend on the use of a phone line like a fax machine does. Additionally,
there is no other end that needs to receive your scanned document in order to complete a
successful transfer.
Using a scanner can also be environmentally friendly that is to say, scanners create digital
copies of documents, photos and files on your computer that you can email to other
people or store and view on your own.
Scanners are very easy to use and the ones that are built into multifunction printers today
can be used essentially without instruction. Most settings are automatically adjusted and
fine-tuned, leaving a user to only select basic options such as photograph or document, or
color versus black and white.
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Disadvantages of scanners
Scanned output varies depending on the quality of the lens inside the scanner, the
cleanliness of the scanner’s glass, and the condition of the original documents.
Scanners are very expensive in terms of buying and maintenance such as replacement of
lambs, and lens etc
Scanners are also relatively slow, so companies and individuals users will need to
consider the time involved in scanning all of their paperwork.
Scanners can be used to fake documents. For example, one of the quickest things that can
be faked with a scanner is an ID.
Most scanners restrict you to the size of an 8.5 inch by 14 inch page of paper, or in some
cases of photo scanners, even smaller. Larger flatbed scanners are expensive, and in most
instances, you’d scan a big document, poster or other item in sections, perhaps even
having to cut or fold it, to completely scan it.
Reading devices
Reading devices are input devices that capture data from a source document, which is the
original form of the data. Examples of reading devices include optical reading devices.
Optical reading devices are devices that use a light source to read characters, marks, and codes
and convert them into digital data that a computer can process.
Examples of optical reading devices include;
Optical character recognition (OCR) Readers
Optical mark recognition (OMR) readers
Bar code readers (BCR’s)
Radio Frequency Identification (RFID) Readers
Magnetic Strip Card Reader
Magnetic Ink Character Recognition (MICR) Readers
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Optical character recognition (OCR) Readers
Optical character recognition (OCR) is a technology that reads typewritten, computer printed, or
handwritten characters from ordinary documents and translates the images into a form that the
computer can understand.
Advantages of OCR readers
They save lot of time when using a digital file rather than paper documents
OCR allows user to copy and paste from the document itself whether that's in PDF format
or MS Word format.
They are less expensive in terms processing documents.
They allow written and printed data to be read at the same time.
Hard copies of documents can be read directly into a computer without retyping.
The characters converted can later be edited by word processing software.
Disadvantages of OCR readers
They are expensive in terms a scanner, OCR software and maintenance.
They are not completely accurate when sending text because it require proofreading
afterwards
Often don‘t work well with hand written characters or those in unusual fonts.
Optical mark recognition (OMR) readers
These are input devices that read hand-drawn marks such as small circles or rectangles. A
person places these marks on a form, such as a test, survey, or questionnaire answer sheet.
The OMR device first reads a master document, such as an answer key sheet for a test, to
record correct answers based on patterns of light; the remaining documents then are passed
through the OMR device and their patterns of light are matched against the master document.
Advantages of OMR readers
They are much faster than someone manually entering large amounts of text
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They consistently provides unmatched accuracy when reading data
They have better recognition rate than OCR hence can read marks.
OMR have large volumes of data that can be quickly collected without the need of
specially trained staff.
Their cost of data input is small.
The chance of data errors can also be reduced because it is not necessary to type the
details for data entry.
Disadvantages of OMR readers
All documents need to be checked over carefully and then manually corrected
If the original document is of poor quality or the handwriting difficult to read, more
mistakes will occur
They are not worthy working for small amounts of text
Documents for OMR are complicated to design.
The OMR reader needs to be reprogrammed for each new document design.
It needs the person putting marks on the documents to follow the instructions precisely.
Any folding or dirt on a form may prevent the form from being read correctly.
A bar code reader
It is an optical reader that uses laser beams to read bar codes by using light patterns that pass
through the bar code lines.
A bar code is an identification code that consists of a set of vertical lines and spaces of different
widths, or a two- dimensional pattern of dots, squares, or other images. The bar code
represents some data that identifies the item and the manufacturer.
Advantages of using Bar Code Reader and Bar Codes
They allow real time data to be collected accurately and rapidly.
Bar code readers enable fast data entry operations with less error.
They are less expensive.
Bar code readers smaller and lighter compared to RFID tags and easy to use.
The process of data entry is fast and accurate.
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Bar codes can be printed by normal printing methods.
No need to write down any key in the name of the item or its accurate price.
Disadvantages of Bar Codes and Bar Code Readers
Barcodes do not have read/write capabilities.
It requires optical line of sight (LOS) scanning.
It is labour intensive as it requires to be scanned individually.
It is less secure compare to RFID which can be easily forged.
It is susceptible to environmental damage.
Scratched or crumpled barcodes may cause problems while scanning.
Only numbers can be coded
Bar codes cannot be read directly by people.
A bar code reader may misread a bar code if there is any dirt or mark on the code.
Radio Frequency Identification (RFID) Readers
Radio-frequency identification (RFID) is a technology that uses radio waves to transfer data
from an electronic tag, attached to an object, through a reader for the purpose of identifying and
tracking the object.
Radio Frequency Identification (RFID) Readers are also used for;
tracking times of runners in a marathon;
tracking location of soldiers,
tracking employee wardrobes,
tracking airline baggage,
tracking misplaced or stolen goods;
gauging pressure and temperature of tires on a vehicle;
tracking payment as vehicles pass through booths on rollway systems;
Checking out library books, etc.
Advantages of Radio Frequency Identification (RFID) Readers
The tag does not need to be in line of sight with the receiver to be read compare to a
barcode reader
RFID tags can store a lot of information, and follow instructions
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They have the ability to pinpoint location
RFID technology is versatile: can be smaller than a thumb tack or can be the size of a
tablet, depending on its use
Disadvantages of RFID Technology
RFID are expensive because of batteries
There still needs to be regulations about RFID guidelines
RFID can be easily intercepted, even if it Encrypted
It takes a lengthy time to program RFID devices
The external electromagnetic interference can limit the RFID remote reading.
The coverage range of RFID is limited which is about 3 meters
Magnetic Strip Card Reader
A magnetic stripe card reader is a reading device that reads the magnetic stripe on the back of
credit cards, entertainment cards, bank cards, gift cards, and other similar cards. The stripe,
which is divided in three horizontal tracks, contains information identifying you and the card
issuer.
Advantages of MICR
The processing speed for cheques are very fast
They are more secure than OCR (Optical character recognition) technology
Documents prepared for MICR are difficult to forge.
Documents can still be read after being folded or split etc.
Disadvantages of MICR
The system can only accept a few characters
MICR readers and encodes are very expensive.
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OCR OMR
Bar code Reader RIFD
Magnetic Strip card Reader MICR
Terminals
Computer terminals are electronic or electromechanical hardware devices that are used for
entering data into, and displaying or printing data from, a computer or a computing system.
The teletype was an example of an early day hardcopy terminal, and predated the use of a
computer screen by decades.
Terminal devices consists of a monitor (output), a keyboard (input), memory, and a video card
often housed in a single unit. A variety of terminals enable both input to and output from a
remote computer system. They are devices that send and receive computer data.
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Categories of terminals
Dumb terminals,
Smart terminals,
Electronic Point of sales (EPOS) terminal
Electronic Fund Transfer Point of Sale (EFTPOS) terminal
Intellectual terminal
A dumb terminal
It is a terminal that has no processing power, thus, cannot function as an independent device.
A dumb terminal can enter and transmit data to, or receive and display information from, a
computer to which it is connected. It connects to a host computer that performs the
processing and then sends the output back to the dumb terminal. The host computer usually is
a server or mainframe.
A Smart terminal
In addition to a monitor and keyboard, a smart terminal also has a processor that has the
capability of performing some functions independent of the host computer.
Electronic Point of sales (EPOS) terminal
This is a type of device used to record purchases at the point where the consumer purchases the
product or service.
Electronic Fund transfer of sale (EFTPOS)
These are terminals capable of transferring funds from customer’s bank account directly to a
retail outlet’s account after reading the customer’s network
Automatic Teller Machine (ATM) is a self-service banking machine that connects
to a host computer through a network. You insert a plastic bankcard with a magnetic
strip into the ATM and enter your personal identification number (PIN), to access
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your bank account. Some ATMs have a touch screen; others have special buttons or
keypads for entering input.
Intellectual terminal
It has a memory and a processor so that it can perform some function independent of
the host computer.
Dump Terminal Smart terminal EPOS terminal
EFTPOS terminal ATM Intellectual terminal
Biometrics input devices
Biometrics is the technology that can be used to authenticate a person's identity by
verifying personal characteristics.
Biometric devices are input devices that translate a personal characteristic into a digital
code that is compared with a digital code stored in the computer. If the digital code in the
computer does not match the personal characteristic's code, the computer denies access to
the individual.
Examples of biometric devices;
A fingerprint scanner
A face recognition system
A voice verification system
A signature verification system
An iris recognition system
Hand geometry system
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A finger
scanner;
A fingerprint scanner is a device that captures curves and indentations of a finger print. Some
grocery and retail stores now use fingerprint readers as a means of payment, where the
customer's finger print is linked to a payment method such as a checking account or credit card.
A face recognition system;
It is a device that captures a live face image and compares it with a stored image to determine if
the person is a legitimate user. Some buildings uses face recognition systems to secure access to
rooms.
Law enforcement, surveillance systems, and airports use face recognition to protect the public.
Some notebook computers use this security technique to safeguard a computer. The computer
will not start unless the user is legitimate.
A voice verification system;
A voice verification system is an input device that compares a person's live speech with their
stored voice pattern.
A signature verification system;
A signature verification system recognizes the shape of your handwritten signature, as well as
measures the pressure exerted and the motion used to write the signature. Signature verification
system uses a specialized pen and tablet.
An iris recognition system;
This is a device highly used in security areas. The camera in an iris recognition system uses iris
recognition technology to read patterns in the iris of the eye.
Iris recognition systems are used by government security organizations, the military and
financial institutions that deal with highly sensitive data.
Finger print scanner Face recognition system Voice verification system
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Signature verification system Iris recognition system Hand geometry system
Advantages of biometric systems:
Improved security
Improved customer experience
Cannot be forgotten or lost
Reduced operational costs
Disadvantages of biometric systems:
Environment and usage can affect measurements
Systems are not 100% accurate.
Require integration and/or additional hardware
Cannot be reset once compromised
Remote control
A remote control (RC) also known as a clicker, flipper, tuner, changer or converter is a small
hand-held electronic device used for controlling other devices, such as a television, radio or
audio/video recording etc. Remote controls commonly operate via infrared signals but sometimes
by radio frequency signals. The remote control controls a variety of functions such as volume,
channel, track number and other functions. Modern remote control devices often have more
controlling functions than are found on the device itself, which may have only a few primary
essential controls.
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Remote control is an input device that emits a beam of infrared light, which carries
data signals. A remote control is primarily a convenience feature for the user, and
can allow operation of devices that are out of convenient reach for direct operation
of controls from a short distance.
Sensor and Remote sensor
A sensor is electronic device which is used to record the present or changes in something for
instance the heat sensor
Remote sensing is the process of detecting and monitoring the physical characteristics of an area
by measuring it’s reflected and emitted radiation at a distance from the targeted area then
converted to electrical signals by sensors which input them to the commuter for processing.
For examples;
1) Cameras on satellites and airplanes take images of large areas on the Earth's surface,
allowing us to see much more than we can stand on the ground.
2) Sonar systems on ships can be used to create images of the ocean floor without needing
to travel to the bottom of the ocean.
3) Cameras on satellites can be used to make images of temperature changes in the oceans.
4) Large forest fires can be mapped from space, allowing rangers to see a much larger area
than from the ground.
5) Tracking clouds to help predict the weather or watch erupting volcanoes, and help watch
for dust storms.
There are two types of remote sensing instruments (sensors);
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Active sensors provide their own source of energy to illuminate the objects they observe.
Passive sensors, on the other hand, detect natural energy (radiation) that is emitted or reflected
by the object or scene being observed.
Various sensors can be used to measure heat, light, pressure, acidity, oxygen concentration,
water flow etc. when the sensors are located at some distance from the computer system, they are
known as Remote sensors.
Storage Hardware’s (devices)
Storage devices also known as storage medium or storage media are hardware components that
write and read data to and from storage media. They are used for storing, porting and extracting
data files and objects. These devices hold and store data, instruction, and information both
temporarily and permanently, and they can be internal or external to a computer, server or any
similar computing device.
The purpose of storage devices is to store data entered before and the results after processing.
Definition of Terminologies used in storage
1. A Storage medium is the physical material on which a computer keeps data. There is a
variety of storage media available.
2. A Storage Device reads and writes data to and from a storage medium.
3. Reading is the process in which a storage device transfers data, from a storage medium
into memory.
4. Writing is the process in which a storage device transfers data from memory to a storage
medium (saving).
5. Access time, is a measure of the amount of time it takes a storage device to locate an
item on a storage medium.
6. Transfer rate is the speed with which data, instructions, and information move to and
from a device. Transfer rates for storage are stated in KBps (kilobytes per second)
7. Throughput is the rate at which the information can be written or read from the storage
device.
8. Storage Capacity is the total amount of data or information (characters) a storage
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medium can hold.
9. Data and information access. Data and information access is either sequential or direct
(Random) access
Sequential Access: In this, data can be accessed sequentially that is one by one from its
location.
Random Access: In this type of access, the data can be accessed directly from its location; this
type of access provides fast access of data.
Types of storage devices
There are two types of storage devices commonly used for storing data, instruction and
information;
1. Primary storage devices
2. Secondary storage devices
Primary storage devices are also known as internal memory or main memory. They are devices
which store data and instructions temporarily for immediate access and use by the computer‘s
microprocessor.
Memory refers to the area or space in the computer where programs and data reside during
computer operations. It is a temporary store or space where instructions to be executed by the
processor and the data to be processed are placed while performing the processing operation.
A computer's memory in the system unit, located physically close to the CPU (to decrease access
time), it provides the CPU with a working storage area for program instructions, data and
information.
Memory usually consists of one or more chips on the mother board or some other circuit board in
the computer. It rapidly provides the instructions and data to the CPU.
Memory stores three basic categories of items:
1. The operating system and other system software that control or maintain the computer and its
devices; 2.Application programs that carry out a specific task such as word processing;
3 The data being processed by the application programs and resulting information.
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Types of computer memory
Volatile memory
Non – volatile memory
Volatile memory
This is the type of memory where the contents or information within the memory are lost when
the computer power is turned off. Random Access Memory (RAM) is an example of a volatile
memory. It is also called Primary memory or Main memory.
Random Access Memory (RAM) is the memory chips that are mounted directly on the
motherboard or mounted on peripheral cards that plug into the motherboard.
Characteristics of RAM
It is a temporary memory.
The user can read from it and write to it.
It loses its contents when power goes off (i.e. it is volatile)
It can be increased.
Functions of RAM
To store data and instructions awaiting processing
It stores the intermediate results of computers working before they are communicated to
their recipients.
It stores instructions which are being obeyed by the computer.
Basic types of RAM
SDRAM (Synchronous Dynamic Random Access Memory)
DRAM (Dynamic Random Access Memory) must be refreshed (or recharged) constantly
by the CPU.
SRAM (Static Random Access Memory) is faster and more reliable than any form of
DRAM. The term static refers to the fact that it does not have to be re-energized as often
as DRAM.
Magneto resistive RAM (MRAM), stores data using magnetic charges instead of
electrical charges.
MRAM has greater storage capacity, consumes less power, and has faster access times.
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Virtual RAM (VRAM): Modern operating systems can use spare storage space on the
hard disk as if it is working memory and this is referred to as Virtual memory or Virtual
RAM
Other terms related to RAM
Cache memory
Cache memory refers to the memory where data and instructions are temporarily held for
immediate access and use by the computer’s microprocessor. A cache is a relatively small block
of very fast memory designed for speeding up the internal transfer of data and software
instructions. It is used to speed up the computing process.
Virtual memory
Virtual memory is a type of memory allocated by the operating system to function as additional
RAM. This portion of storage medium is usually got from the hard disk. The area of the hard
disk used for virtual memory is called a swap file.
A buffer;
A buffer is an area of memory or storage in which data and information is placed while waiting
to be transferred to or from an input or output device.
There are two forms of buffer
Input buffer; is used between the input device (the sending device) and the CPU (the receiving
device). The role of the input buffer is to accept data/instructions at the speed of input device,
which is comparatively slow, and remits them at the high speed of the CPU as computer inputs.
Low speed High speed
Output buffer; the output buffer is used between the CPU and the output unit. The role of the
output buffer is to accept data and instructions at the high speed of the CPU and remits them at
the low speed of the output device, to go as computer outputs.
High speed Low speed
N.B: Buffering refers to the process of using the buffer to control the speed of communication
between the CPU and peripheral devices.
Importance of the buffers
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Input device CPU
Output put device
Input Output buffer
Input buffer
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They help the operating system to carefully monitor the contents in memory.
It helps the operating system to clear these items from memory when they are no longer
required by the CPU.
Spooling
Spooling is the process of placing print jobs in a buffer instead of being sent immediately to the
printer.
Non – Volatile memory
Non volatile memory is a type of memory where contents within the memory are not lost when
power is removed from the computer. Example of a non volatile memory is Read Only Memory
(ROM)
READ ONLY MEMORY (ROM)
Read-only memory (ROM) refers to memory chips storing permanent data and instructions. The
items stored in ROM chips cannot be modified
ROM is a non – volatile, permanent type of memory found in the computer that is to say the
contents of this memory cannot be irremovable and unchangeable.
ROM chips contain permanently written data, instructions, and information recorded by
manufactures which are called firm ware. Firmware allows the computer user to read and used
information, but cannot change anything.
Characteristics of ROM
The user can read the contents of ROM but can‘t make modifications or write to it.
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It is a permanent memory
It is a non – volatile memory.
It cannot be increased.
Types of ROM
Programmable Read Only Memory (PROM)
It is a kind of memory which can only be programmed once after it has been manufactured. Once
the data and instructions are programmed into PROM chip, the chip functions like a regular
ROM and cannot be erased or changed. It is common with CD – W (Compact - Disk Writable)
Electronically Programmable Read Only Memory (EPROM)
Is a kind of memory on which instructions can only be erased once and then reprogrammed.
Afterwards, the reprogrammed instructions can never be altered. It is common with compact disk
re –writable.
Electronically Erasable Programmable Read Only Memory (EEPROM)
It is a type of memory that enables a user to store information on it as many times as one may
desire.
The instructions remain in memory until when one may wish to alter them. It is common in
applications such as most color TVs to store TV settings such as color, contract, brightness, and
Mobile phones to store phone numbers etc
Other terms related to ROM
BIOS (Basic Input / Output System)
It resides in the ROM. It is a sequence of instructions the computer follows to load the operating
system and other files when the computer is turned on.
CMOS (Complementary Metal Oxide Semiconductor)
It is used to store configuration information about the computer. This information includes; the
amount of memory installed, types of disk drives, the types of keyboard, monitor, current date
and time e.t.c.
CMOS technology uses a CMOS battery power to retain its information even when the computer
is turned off. Its contents can be changed. It provides high speeds and consumes little power.
Flash Memory
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Flash memory is a chip that keeps its memory when the power is shut off. It can be erased
electronically and reprogrammed. Most computers use flash memory to hold their start-up
instructions because it allows the computer easily to update its contents. Flash memory chips
also store data and programs on many mobile computers and devices, such as; Smart telephones,
Digital cameras, pagers, PDAs, Automotive devices, portable media players, digital voice
recorders, and printers, etc.
Video memory Video memory or video RAM (VREAM) chips are used to store display images for the monitor.
The amount of video memory determines how fast images appear and how many colors are
available.
Differences between RAM and ROMRAM ROM1. Volatile, temporally 1.Non Volatile, permanent
2. Contents lost when power goes off 2. Contents remain when power goes off
3. Read and Write 3. Read Only
4. Can be increased 4. Can’t be Increased
5. Not installed at Factory 5.Installed at Factory
Secondary storage devices refer to the storage media designed to retain data, instructions, and
information in a relatively permanent form. These devices are non volatile that is to say they
save data and remain intact even if the computer is turned off.
These usually have large storage capacity, and they store data permanently. They can be both
internal and external to the computer, and they include the hard disk, compact disk drive and
USB storage device.
Categories of secondary storage devices
Secondary storage devices are categorized into three groups;
Magnetic storage devices
Optical storage devices
Solid state storage devices
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Magnetic storage devices
Magnetic storage devices are storage devices that use a magnetic head to write
data to and from a magnetized medium. Magnetic storage medium can be as
basic as a plastic tape that is coated with fine particles of a metal like the ones
found in audio recording devices.
Examples of magnetic storage devices include:
i. Magnetic tape
ii. Floppy disk,
iii. Zip and Jaz disks
iv. Hard disks
Magnetic tape
Magnetic tape is a magnetically coated ribbon of plastic capable of storing large amounts of
data and information at a low cost. Tape storage requires sequential access, i.e. data must be
accessed in the order in which it is stored. If the computer is to read data from the middle of a
tape, all the tape before the desired piece of data must be passed over consecutively. Today,
magnetic tape storage is no longer used for routine processing. To read or to write the
information in a tape, the read/write head of the tape used in which the tape rolls.
Advantages of
magnetic tapes
Magnetic tape cartridge can store large amounts of data and information up to 1 Terabyte.
Data collection can go on without interruption overnight or for an entire weekend.
Magnetic tape can be recorded over and reused repeatedly.
Magnetic tape is inexpensive and budget friendly.
Its storage is large than that of floppy disks.
It is light and portable
Disadvantages of magnetic
tapes
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Special equipment must be purchased and set up for recording and storing data. The data
can only be read on the special equipment.
If the data is stored near a strong magnetic field or a large speaker, the tape can be
damaged.
Magnetic tape has a lifespan of 15 years. Data quality gradually erodes over time.
It is necessary to keep older tape equipment just to be able to read the stored data.
Data access is only sequential which is time wasting. That is Random data access is not
possible
Floppy disks (diskettes)
A floppy disk is a portable in expensive storage medium that consist of a thin, circular, flexible
plastic disk with a magnetic coating enclosed in a square – shaped plastic shell. They can be read
from and written to using a Floppy Disk Drive (FDD). The drive is usually designated letter A
(for a computer with only one drive).
Formatting of storage media
Formatting is the process of preparing a disk for reading and writing by organizing the disk into
storage locations called tracks and sectors.
Reasons for formatting a disk
When the disk space is full
During fresh installation
When operating system is corrupted on a disk
In case of virus infection
Procedures of formatting a disk
Click on the start button
From the options choose and click my computer
Choose on the desired disk and right click
From the popup menu click format
Then click start button
Care for floppy diskettes
- Avoid touching the disk surface
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- Avoid bending them or putting weights on them
- Avoid exposing them to sun or heat and cold
- Keep them in dust free environments
- They should not be exposed to chemicals such as cleaning solvents.
- Keep the diskettes in their jackets.
Advantages of floppy disks
They are portable
They are cheap
Data on a floppy disk can be accessed randomly
Data on a floppy disk can be writing – protected from being changed accidently.
They can be used to transfer data from one computer to another.
Disadvantages of floppy disks
They provide less storage capacity of 1.44MB (about 500 double-space pages
of text, several digital photographs, or a small audio file) compared to the hard
disks.
They are not durable
They can easily be damaged by magnetic fields
They operate at a low speed
Can easily be lost or misplace because of their size.
They can easily infect machines with viruses.
Zip drive
The Zip drive is a medium-capacity removable disk storage system with capacities of 100 MB to
750 MB that was introduced by Iomega in late 1994. These are storage devices that were made to
store medium amount of data. Their capacity is bigger than that of floppy disks. Data access is
random /direct. They have got a faster transfer rate.
Hard disk (Fixed disk/Hard driver)
This is a metallic magnetic media housed in an air tight rigid box, found inside the computer
system unit to avoid contamination. .It is a secondary storage device that consists of one or more
platters to which data is written using a magnetic head, all inside of an air-sealed casing. A hard
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disk is a non-volatile memory hardware device that permanently stores and retrieves data on a
computer.
Internal hard disks reside in a drive bay, connect to the motherboard using an ATA, SCSI,
or SATA cable, and are powered by a connection to the power supply unit
Types of Hard Disk
Internal hard disk is a type of hard disk fixed in the system unit and usually stores the operating
system required for the computer to work.
External hard disk is a separate free-standing hard disk that connects with a cable to a USB
port or FireWire port.
A removable hard disk is a hard disk that you insert and remove from either a dock or a drive.
An Internet hard drive, also called online storage, is a service on the Web that provides storage
to computer users, usually for a minimal monthly fee.
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Parts of a hard disk
Platter: It is the area where information is written to the disk. It spins constantly as it continues
to add important data to the computer hard disk
Spindle: It helps to hold the platter in order to enable it to rotate/spin at the necessary speed
Head: It is a form of magnet that helps in recording information to the hard disk drive.
Actuator: Its use is to read and record information continuously.
Actuator arm: it allows the head to move back and forth across the disk drive as it records
information.
Actuator Axis: It allows the actuator arm to move back and forth easily.
Jumper block: Allows a cable to be connected to the power supply of the computer and to the
mother board of a computer system.
Integrated Drive Electronics (IDE) connector: Allows a cable to run from the hard disk drive
to the motherboard of the computer system.
Power connector: It provides power from the power supply
Advantages of hard disks
They provide a greater storage capacity
They are speedy i.e. the time of data access is very fast and convenient
They are cheaper than floppy disks per megabyte.
They are more reliable than floppy disks.
There are fewer chances of being misplaced because they reside
inside the system unit
The life of hard disks is quite long once in use.
Disadvantages of hard disks
They are bulky (not portable)
They are susceptible to virus attacks especially in unprotected systems.
Since they are metallic, they expand and contract depending on the temperature
changes which may lead to data loss.
May easily fail due to violent shaking(vibration)
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Magnetic tape Floppy disk
Zip & Jaz disks Hard disk
Optical storage devices
Optical storage is any storage method in which data is written/ recorded and read by
making marks in a pattern that can be read back with the aid of light, usually a beam
of laser light using optical discs for archival or backup purposes. The reflected light
is converted into a series of bits that the computer can process.
Optical discs (devices) are flat, round, portable storage medium made of metal, plastic, and
lacquer that is written and read by a laser. N.B A lacquer is a liquid which is painted on wood or
metal and forms a hard, shiny, protective surface when it dries
In optical technology, a laser hits a layer of metallic material spread over the surface
of a disk. When data is being entered, heat from the laser produces tiny spots on the
disk surface. To read the data, the laser scans the disk, and a lens picks up different
light reflections from the various spots.
Categories of optical discs
Optical discs are categorized into three general categories;
Compact disks (CDs)
Digital Video Discs (DVDs)
Blue-ray disks
Notice: DVDs have much greater storage capacity than CDs.
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Compact disks (CDs)
Compact disks are flat, round, portable, storage medium usually with a diameter of 12cm and
thickness of a few millimeters. The CD is designated by a letter D for the hard disk is C
Characteristics of compact disks
They store items by using microscopic pits and land that are in the middle layer of the
disk.
Data access is random /direct.
They have very fast access time.
Data transfer rate is very high.
The contents of standard CDs are written by the manufacturer and only can be read and
used.
A typical CD holds from 650 MB to 1GB of data,
Advantages of compact disks
More portable than a hard disk
Has relatively large storage (650-700MB) than diskettes
They are easy to store
They have a very fast access speed.
They are not easily attacked by viruses
Disadvantages of compact disks
Any single scratch or breakage on a CD can render the whole CD useless.
Most CDs are read only.
Care for compact disks
Always store the CD in its jacket (jewel box) when not in use.
Always hold a compact disk by its edges.
Never touch the underside of the CD
Never stack disks on top of each other
Never expose CDs to excessive heat or sunlight.
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TYPES OF COMPACT DISKS
CD –ROM
CD –R
CD –RW
Photo CD
CD – ROM (Compact Disk - Read Only Memory)
Compact Disk - Read Only Memory is a type of optical disc that users can read but not write or
erase-hence, the name read-only. The contents of standard CD-ROMs are written or recorded by
the manufacturer and can only be read and used. Contents of a CD – ROM can‘t be modified.
CD – R (Compact Disk -Recordable)
CD-R (compact disc-recordable) is a technology that allows you to write on a compact disc using
your own computer’s CD-R drive. Once you have recorded the CD-R, you can read from it as
many times as you desire. A CD-R is a multisession optical disc which allows you to write on
part of the disc at one time and another part at a later time. However, you cannot erase the disc's
contents.
CD – RW (Compact Disk -Rewritable)
Compact Disk -Rewritable is an erasable compact disk that can be written on multiple times; to
write on a CD-RW, you must have a CD-RW drive and CD-RW software.
A Picture (Photo CD)
A photo compact disk is a type of disk that contains only digital photographic images saved in
the jpg file format; A Picture CD is a multisession disc, i.e. you can write additional data to the
disc at a later time.
The images on a Picture CD can be printed, faxed, sent via electronic mail, included in another
document, or posted to a Website. Many people use Picture CD to preserve their photos.
Qn. Differentiate between a disc and a disk
A ‘Disc’ refers to optical media, such as CD, CD-R, DVD-R, DVD-RW, etc. These are a type of
removable storage devices that can be used to store files, songs, etc. Some of these files are read-
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only (ROM), while others allow users to burn content on it either once or multiple times,
depending on the type. These ‘discs’ are removable, meaning they can be removed or ejected
from the computer.
A ‘Disk’ is a magnetic storage device, similar to floppy disks, the disk on the computer’s hard
drive and an external hard drive. These disks are usually sealed within a plastic or metal case in
order to protect the magnetic files on it from damage. Disks are rewritable, unless they are
locked by the administrator. Disks such as the hard drives on the computer can be partitioned
into smaller volumes. Hard drives are not removable from the computer, though floppy disks and
external hard drives do not need to be placed inside the computer and can be removed.
Digital Video/ Versatile Discs (DVDs)
Digital Video/ Versatile Discs (DVDs are flat, round, portable, storage medium usually with a
diameter of 12cm and thickness of a few millimeters with high capacity storage from 4.7GB to
17GB than compact discs. They are widely used for storing and viewing movies and other data.
Types of Digital Video/ Versatile Discs (DVDs);
DVD –ROM
DVD –R
DVD +RW
DVD-RAM
Digital video disc-Read Only memory (DVD-ROM);
Digital video disc-Read only memory (DVD-ROM) is an extremely high capacity compact disc
capable of storing from 4.7 GB to 17GB; In order to read a DVD-ROM, you must have a DVD-
ROM drive, which can also read CD ROMs.
DVD – RAM (Digital Video Disk - Random Access Memory)
Digital Video Disk - Random Access Memory is a recordable and rewritable version of DVD –
ROM, which allows items to be erased and recorded on it multiple times.
DVD – R (Digital Video Disk -Recordable)
Digital Video Disk -Recordable is a recordable and rewritable version of DVD – Rom which can
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be written once and read for many times.
DVD – RW (Digital Video Disk -Rewritable)
Digital Video Disk -Rewritable is a recordable and rewritable version of DVD – ROM which can
be written and read for many times.
Blue-ray disks
Blue-Ray disks are a
recent replacement for DVDs. A Blue-Ray disc can hold 25 - 50GB of data (a dual-layer. Blue-
Ray discs are random-access devices.
They are used in the same way as DVD-ROMs but, since they can hold more data, they are also
used to store very high-quality, high-definition (HD) video.
The 'Blue' part of Blue-Ray refers to the fact that the laser used to read the disc uses blue light
instead of red light. Blue light has a shorter wave-length than red light (used with CDs and
DVDs).
Using a blue laser allows more data to be placed closer together on a Blue-Ray disc, than on a
DVD or CD, so Blue-Ray has a much higher storage capacity than these older discs.
Solid state storage devices
The term ‘solid-state’ essentially means ‘no mechanical or moving parts’ it is abbreviated
as “SSS”
Solid state storage devices are non-volatile computer storage devices that are made from silicon
microchips used to store and retrieve digital information electronically without any involvement
of moving or mechanical parts.
They differ fundamentally from the traditional electro-mechanical storage devices that read and
write data from a rotating magnetic disk.
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Characteristics of solid state storage devices
They have no mechanical or moving parts
They are non volatile devices
They operate much faster than traditional electromechanical storage devices
They consume less power and are more resilient under physical shock.
They are very expensive
They are built on flash memory architecture
They provide a temporary storage solution for portable information.
Solid State devices provide a quick, easy, and accessible way to gather, add, and
temporarily store genealogical information until it may be organized and stored in more
permanent formats.
There are three forms of solid state storage
Solid state drives
Solid state cards
Solid state modules
Solid state drives
A solid state drive is a type of mass storage device similar to a hard disk drive (HDD). It
supports reading and writing data and maintains stored data in a permanent state even without
power. Internal SSDs are connected to a computer like a hard drive, using
standard IDE or SATA connections.
Instead of storing data on magnetic platters, SSDs store data using flash memory. Unlike hard
drives, SSDs do not have any moving parts (which is why they are called solid state drives).
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The most commonly used solid state drive is USB flash memory drive (disk)
A USB flash drive is a flash memory storage device that plugs in a USB port on a computer.
USB flash drives are convenient for mobile users because they are small and lightweight enough
to be transported in a pocket.
Current USB flash drives have data storage capacities ranging from 256 MB to 64 GB. USB
flash drives have become the mobile user's primary portable storage device
Solid state cards
Solid state cards are non-volatile cards without moving or mechanical parts that supports reading
and writing data and maintains stored data in a permanent state even without power.
Examples of solid state cards are;
A punch card
Flash memory card
Smart card
A punched
A punched card also known as IBM card or Hollerith card is a piece of stiff paper that contains
digital information represented by the presence or absence of holes in predefined positions.
It is a flat card which consists of rows of numbers and letters neatly arranged in columns. To
store data, the card is inserted in a computer drive and then the computer punched a series of
holes in the rows of characters to represent the data stored. It has a very low transfer rate. It has
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much access time, and data access is sequential.
Fig: A punched
card
Flash memory cards
Flash memory cards are tiny re-recordable solid-state devices with no moving parts capable of
retaining data without power. They are commonly used in electronic devices such as digital
cameras and mobile phones. They have transfer rates range from about 1 MBps to 20 MBps or
more.
A smart card
A smart card is similar in size to a credit card. It stores data on a thin microprocessor embedded
in the card. A smart card contains a processor and has input, process, output, and storage
capabilities. When the smart card is inserted into a specialized card reader, the
information on the smart card is read and, if necessary, updated.
Solid state modules
Solid state modules are solid state storage that resides in a Dual In-line Memory Module
(DIMM) or similar form factor. Solid state modules devices are physically smaller in size than
solid state cards; they have lower storage capacity normally used in mobile devices.
Examples of solid state modules include;
Microfilm Microfiche
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Photographic film
Microfilms
These are media used to store microscopic images of documents on roll or sheet film. The
images are recorded onto the film using a device called a computer output microfilm recorder.
The stored images are so small they can be read only with a microfilm or microfiche reader.
Microfilm is a 100- to 215-foot roll of film.
Microfiche
Microfiche is a small sheet of film, usually about 4 × 6 inches. The images are recorded onto the
film using a device called a computer output microfilm recorder. The stored images are so small
they can be read only with a microfilm or microfiche reader.
N.B Microfilm and microfiche have the longest life of any storage medium.
Photographic film
Photographic film is a sheet of plastic such as polyester coated with a light sensitive emulsion
that is used to record and store photographs.
Difference between primary storage and secondary storage
Primary storage Secondary storage
Memory is directly connected t and accessed by
CPU
Memory not connected to CPU
Memory is volatile Memory is non volatile
RAM is directly installed onto a motherboard Hard disk drive is connected to the motherboard by a cable
There is direct access by the CPU There is indirect access by the CPU
Data access is faster Data access is slower
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Used for processing data Used for storing data
They are small in size They are lager is size
Units of Measuring Computer Memory
The smallest unit of measuring Computer Memory is a Binary digit (Bit). Binary digits are the
numbers 1 and 0 which can be represented in a computer by switching voltage on and off. Eight
little bits make one BYTE.
Definitions;
Bit;
A bit is the smallest unit of measurement of computer memory. Each 0 or1 is called a―Bit
Nibble
A nibble is a group of four (4) binary digits
Byte;
A byte is a group of eight binary digits. It is the fundamental (basic) unit for measuring
computer’s memory.
A kilo byte (KB);
A kilo byte is a group of 1000 bytes (or exactly 210 or 1024bytes)
Megabyte (MB);
A mega byte is a group of 1,000,000 bytes (or exactly 220bytes)
Giga byte (GB);
A Giga byte is a group of 1,000,000,000 bytes (or exactly 230bytes)
Terabyte (TB);
A Terabyte is a group of one trillion bytes
(240bytes)
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Converting from binary to decimal
Multiply each bit of the binary number by its corresponding bit-weighting factor. Sum up all of
the products in step (a) to get the decimal number.
E.g.: Covert 1011 binary to Decimal
Soln: 1011 binary = 1x23 + 0x22 +1x21 +1x20 +
= 8+0+2+1
= 11
Converting from decimal to binary
Divide the decimal number by 2; and record the remainder. If the quotation is zero, the
conversion is complete. Otherwise repeat step (a) using the quotation as the decimal number. The
new remainder is the next most significant bit of the binary number. E.G.: Convert 11 decimal
to binary
2 11 1
2 5 1
2 2 0
2 1 1
0 0 0
=1011
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PROCESSING DEVICES
Processing devices are devices that work together in gathering, decoding, executing and
outputting of information to the computer user. They are the computer electronic components
and chips houses in the system unit. The most important processing device is the central
processing unit.
Central Processing Unit
Central Processing Unit (CPU) is the most important component of a computer system that is
commonly referred to as the "brains" or the “Heart” of a computer because it monitors all the
computer operations; it is also called the processor or microprocessor.
Central Processing Unit (CPU) therefore means an electronic device that interprets and carries
out the basic instructions that tell the computer how to work. The CPU in other words controls
and coordinates the activities of all the other components of the computer system and performs
all the arithmetic and logical operations to be applied to the data.
Functions of a central processing unit (CPU)
1. It controls devices under its care
2. It helps in all stages of data processing
3. It performs logical computations & comparison of data
4. It determines how fast a computer performs a function
5. It is used as a yardstick to determine the type & the model of the computer
6. It helps the user to work with many programs at the same time.
7. It stores data temporarily for the computer
Types of central processing unit (processors)
Pentium Pro
Pentium II
Pentium III
Intel Core
Intel core 2
Core 2 quad
Celeron M
AMD Dual core
Intel Pentium Dual core
Parts of central processing unit
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The CPU is made up of three main components/parts;
1) Control unit
2) Arithmetic and Logic Unit (ALU)
3) Registers ( Memory)
Control unit
The control unit is a group of electronic circuitry that has the overall function of directing and
controlling and coordinating most of the operations within the central processing unit.
It extracts instructions from memory and decodes and executes them. In fact it regulates the flow
of information through the processor. In short, it can be said, this component receives, decodes,
stores results and manages execution of data that flows through the CPU. Its communication
with both arithmetic unit and memory is inevitable.
Functions of the control unit;
Interpreting each instruction issued by program and then initiating the appropriate
action to carry out the instruction.
Directing data from storage to memory.
Sending data required for mathematical operations from the memory to the ALU.
Sending the data processed to the printer or a storage device.
Erasing/deleting/rubbing data from memory when instructed to do so.
Storing results in the CPU memory.
Machine cycle
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A machine cycle is a series of operations performed to execute a single program instruction. For
every instruction, the control unit repeats a set of four basic steps that s. These four basic steps
include;
1. Fetching
2. Decoding
3. Executing
4. Storage
Step 1: Fetching. The control unit obtains /gets/fetches instruction to be executed from memory
(RAM).
Step 2: Decoding which means to interpret and understand the meaning of given information.
The control unit after receiving instructions, the instruction is then interpreted and translated into
commands the computer understand. Relevant data is moved from memory to the register, and
the location of the next instruction is identified.
Step 3: Executing. Carrying out commands by the given control and performing the actual
operation on the data such as arithmetic computation and logical comparison by ALU.
Step 4: Storage. Storing results into registers or memory
Notice: The first two steps are called instruction time (I-time), and the last two steps are called
execution time (E-time)
Arithmetic Logic Unit (ALU)
Arithmetic Logic Unit (ALU) is an electronic circuitry that executes all arithmetic and logical
operations. Its function is to perform arithmetic calculations such as addition, subtraction,
multiplication and division as well as comparisons. The unit also compares numbers, letters, or
special characters. There can be more than one Arithmetic logic unit in a CPU, and these ALUs
can also be used for the purpose of maintaining timers that help to run the computer.
Program registers (Memory Unit)
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Register is a circuitry that acts as the main store, internal store or intermediate access storage
used to store data within the CPU while the computer is processing functions.
Register is a temporary storage area within the CPU which is responsible for holding data and
instruction to speed up processing.
Register is a part of the processor, not a part of memory or a permanent storage device. They are
additional storage locations that offer the advantage of speed.
Types of registers and their roles
1. Instruction register, which contains the instruction being executed;
2. Address register, which keeps track of where a given instruction or piece of data is
stored in memory.
3. Storage register, which temporarily holds data taken from or about to be sent to
memory.
4. Accumulator, which collects the result of computations;
5. General-purpose register, which is used for several functions, such as arithmetic
operations.
OUTPUT DEVICES
Output is data that has been processed into a useful form called information. Output can be in a
form of text, graphic, audio, and video.
Text consists of characters (letters, numbers, punctuation marks, or any other symbol requiring
one byte of computer storage space) that are used to create words, sentences, and paragraphs.
Graphics are digital representations of non-text information such as drawings, charts,
photographs, and animation (a series of still images in rapid sequence that gives the illusion of
motion).
Audio is music, speech, or any other sound.
Video consists of images played back at speeds to provide the appearance of full motion.
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Output from a computer can either be is a hardcopy form or a softcopy form.
Hardcopy
A hardcopy is permanent reproducible information from a computer printed on printed materials
such as computer prints out, tale printer pages, fax pages, etc.
Advantages of a hardcopy
It cannot easily be changed without trace.
It can be read off-line without a computer.
It doesn‘t require computer devices in order to read the output hence becoming cheap.
Hardcopies last longer if stored in a safe place compared to a softcopy which must all
the time be changed with the technological developments taking place.
Hardcopies cannot be attacked by viruses as the case with the softcopy.
Disadvantages of a hard copy
It Is Expensive.
It Is Difficult To Store.
Other Users Can Make Copies Of The Hard Copy.
It Is Not Environmentally Friendly
Soft copy
A soft copy is the unprinted digital document file. It can be viewed through appropriate editing
programs like word processor, data base programs, presentation soft ware. It can also be moved
from one computer to another through a file transfer.
Advantages of soft copy
They are not presented physically
They only exist on the computer hard drive
They are used for personal purposes
They can easily be converted into a hard copy
They are less costly
Disadvantaged of soft copy
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Information can easily be manipulated.
It cannot be read without a computer.
It requires computer devices in order to read the output.
Softcopy changes all the time when the technological development is taking place.
Softcopy can easily be attacked by viruses.
Output devices are devices used to bring out information from the computer and present it in a
suitable form to the user.
Examples of output devices;
Display devices
Printers
Speakers
Headsets
Earphones
Fax machines
Multifunction peripherals
Data projectors
Interactive whiteboard
Terminals
3D-spectacles
Display devices
Display devices also known as Visual Display Units (VDUs) are output devices that visually
convey text, graphics, and video information to the user. Information’s shown on a display
device are known as soft copy.
Examples of display devices include;
Liquid Crystal Display (LCD) monitors
Cathode Ray Tube (CRT) monitors.
Plasma monitors
Data projector
Head mounted display /A head gear
Light emitting diode (LED)
Liquid Crystal display (LCD monitor)
A liquid crystal display (LCD) monitor is a computer monitor or display that uses LCD
technology to show clear images, and is found mostly in laptop computers and flat panel
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monitors.
They are available in a variety of sizes, with the more common being 17, 19, 20, 22, 24, 27, 45
or 65 inches. Many LCD monitor have wide screen, which are much wider than they are tall.
Advantages of LCD Monitors
They require little power.
They take up less desk space than CRT.
They emit very little radiation.
They are portable than CRTs
Disadvantages of LCD Monitors
They are very expensive than CRT monitors
They can only be viewed from a very narrow angle.
LCD color output is usually slow and poor
Factors that affects the quality of an LCD monitor
i) Resolution
ii) Response time,
iii) Brightness,
iv) Dot pitch,
v) Contrast ratio.
i) Resolution is the number of horizontal and vertical pixels in a display device. A pixel is a
single point in an electronic image.
A higher resolution uses a greater number of pixels and thus provides a smoother, sharper,
and clearer image.
ii) Response time of an LCD monitor or screen is the time in milliseconds (ms) that is takes
to turn a pixel on or off.
iii) Brightness of an LCD monitor or screen is measured in units.
A nit is a unit of visible light intensity equal to one candela (formerly called candlepower)
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per square meter.
The candela is the standard unit of luminous intensity.
iv) Dot pitch, sometimes called pixel pitch, is the distance in millimeters between pixels on a
display device.
v) Contrast ratio describes the difference in light intensity between the brightest white and
darkest black that can be displayed on an LCD monitor.
A Cathode Ray Tube (CRT) monitors
A CRT (cathode ray tube) monitor is a desktop screen that contains a large sealed glass cathode-
ray tube. Inside the CRT, an electron beam moves back and forth across the back of the screen.
This causes dots on the front of the screen to glow, producing an image on the screen. Each dot
consists of a red, a green, and a blue phosphor, which combine to make up a pixel.
Advantages of CRT monitors
They operate at any resolution, geometry and aspect ratio without the need for
rescaling the image.
CRTs run at the highest pixel resolutions generally available.
Produce a very dark black and the highest contrast levels normally available.
CRTs produce the very best color and gray-scale and are the reference standard for all
professional calibrations.
CRTs are best for rapidly moving or changing images
Can produce fast and rich color output.
Can be viewed from a very wide angle.
They are cheaper than the LCD.
Disadvantages of CRT monitors
They are subjected to geometric distortion and screen regulation problems.
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They are relatively bright but not as bright as LCDs. Not suitable for very brightly lit
environments.
Some CRTs have a rounded spherical or cylindrical shape screen.
CRTs give off electric, magnetic and electromagnetic fields that pose a health hazard
They are large, heavy, and bulky. They consume a lot of electricity and produce a lot of
heat.
A plasma monitor
This is a display device that uses gas plasma technology, which sandwiches a layer of gas
between two glass plates. When a voltage is applied, the gas releases ultra violet (UV) light. This
UV light causes the pixels on the screen to glow and form an image.
Advantages of plasma monitors
1. They can be mounted on the wall
2. They are less bulky than rear-projection televisions
3. They produces deep blacks allowing for superior contrast ratio
4. They have a wider viewing angle than those of LCD
5. They are less susceptible to reflection glare in bright rooms
6. Plasma monitor offer screen sizes up to 60 inches wide.
7. Have a richer color display than LCD monitors.
Disadvantages of plasma monitors
1. They have heavier screen-door effect compared to LCD or OLED based TVs.
2. Susceptible to screen burn-in and image retention
3. Susceptible to "large area flicker".
4. Generally do not come in smaller sizes than 37 inches.
5. Heavier than LCD due to the requirement of a glass screen to hold the gases
6. Use more electricity, on average, than an LCD TV
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7. Do not work as well at high altitudes due to pressure differential between the gases inside
the screen and the air pressure at altitude.
8. They are more expensive.
Data projectors
A data projector is an output device that can take images generated by a computer and
reproduce them onto a screen, wall, or other surface so that an audience of people can see the
image clearly. For example, you could use a projector to show a presentation on a large screen
so that everyone in the room can see it.
There are three types of data projectors;
A liquid crystal display (LCD) projector
A digital light processing (DLP) projector
Cathode ray Tube projector
Applications of data projector today
Project a PowerPoint presentation at a business meeting.
Project a computer screen to teach a class in school.
Project a TV or computer with a movie playing to a large screen.
Demonstrate a product or service at a convention center.
Transform a wall, house, or other object to give it a different appearance.
Head mounted display (HMD) / headgear
A headgear is made up of two tiny display and sound systems that channel images and sound
from the source to the eyes and ears, thus presenting a stereo three dimensional sound effect in
the virtual world. The wearer may also put on a body suit that senses the body movement and
relays the data into the virtual reality system which in turn adjusts the position of the user in the
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system.
Light Emitting Diode (LED) displays
Light emitting diode is a flat panel electronic device that emits light when an electrical current is
passed through it. They are typically used outdoors in store signs and billboards.
LEDs are commonly used for indicator lights (such as power on/off lights) on electronic devices.
They also have several other applications, including electronic signs, clock displays, and
flashlights. Some examples include street lights, the red lights on cars, and various types of
decorative lighting. You can typically identify LEDs by a series of small lights that make up a
larger display.
Advantages of display devices (Visual Display Unit)
Their time to display the image is fast.
Their screen displays can include text, graphics and colors.
Display devices are usually quiet.
No paper is wasted for obtaining the output.
Disadvantages of display devices (Visual Display Unit)
Information produced on the screen is only temporary and will be lost when the
power of the device is off.
Un suitable for users with display problems
Needs a separate device (Such as a printer) to produce the hardcopy
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Printers
A printer is an external hardware output device that takes the electronic data stored on a
computer or other device and generates a hard copy of it on a standard size sheet of paper.
Printers are one of the most popular computer peripherals and are commonly used to print text
and photos.
Printers differ in terms of speed, storage, features, quality, and capabilities are available in a
range of prices.
CATEGORIES OF PRINTERS;
Character printers
Line printers
Dot matrix printers
Page printers
Daisy wheel printers
Braille printer
Impact Printers
These are printers that produce a hard copy output by the print heads physically touching the
print media. Print media include paper, transparencies, cloths, some plastics, etc. Impact
printers form characters and graphics on a piece of paper by striking a mechanism against an
ink ribbon that physically makes contact with the paper.
Examples of impact printers include;
Character printers
Line printers (High speed printers)
Dot matrix printers
Page printers
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PRINTERS
Inkjet printers
Photo printers
Laser jet printers
Label printers
Plotters
Mobile printers
Thermal printers
IMPACT PRINTERS NON-IMPACT PRINTERS
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Daisy wheel printers
Braille printers
Character printers
Character printers are types of printers that print one character at a time instead of one line at a
time. Character printers are rarely used today because of speed issues and because only text is
capable of being printed.
Line printers
A line printer also known as a band printer, chain printer, drum printer, and barrel printer is an
impact printer that prints one line of text at a time or entire line of text at once from one end of a
paper to the other end.
These types of printers are too fast to be measured in words or characters per minute, and in lines
per minute. For example, a line printer may be capable of printing over 3,000 lines of text per
minute
Dot Matrix Printers
Dot matrix printers are types of printers that produces characters and illustrations by striking pins
against an ink ribbon like in a type writer to print closely spaced dots in the appropriate shape.
Dot-matrix printers are relatively expensive and do not produce high-quality output
Page printers
Page printers are printers which processes and print a whole page at a time, as opposed to
printers which print one line or character at a time such as line printers and dot-matrix printers.
A page printer is a printer that prints one full page of text or graphics at a time, ejects that page
and then feeds in the next page to be printed. They are much faster than all other printers.
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Daisywheel printer
Daisy wheel printers are printers consisting of a wheel and attached extension on which molded
metal characters are mounted. When it is printing the wheel rotates until the right character is
facing the paper. They produces quality texts but cannot produce graphics output. Printing
different types of font is impractical since the wheel has to be changed to get a different font
Braille printers
Braille printers are impact printers that create tactile dots on heavy paper, making written
documents accessible to blind individuals. They press dots down onto a piece of paper to let a
person using the Braille system read by using their fingers.
A Braille embosser is a device that connects to a computer to produce printed material in the
Braille writing system. They need special Braille paper which is thicker and more expensive than
normal paper. Once a copy produced, printing further copies is often quicker by means of a
device called a "thermoform", which produces copies on soft plastic.
Character printer Line printer Dot matrix printer
Page printer Daisy wheel printer Braille printer
Braille paper
Advantages of impact printers
They are easy to maintain (can withstand dusty environments, vibrations and high
temperatures)
They are more flexible and inexpensive.
They print various styles and heavy graphics.
They have a longer life span. Can print over 100 million characters in their lifespan.
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Disadvantages of impact printers
They are noisy during operation.
They tend to overheat up especially during long printouts.
They have a lower print resolution compared to non – impact printers.
Their printing speed is too low.
They require special form of paper.
Non – impact printers;
These are printers that produce characters and graphics on a piece of paper without the
print heads physically touching the printing surface.
Examples of non-impact printers include;
Inkjet printers
Photo printers
Laser jet printers
Label printers
Plotters
Mobile printers
Thermal printers
Inkjet printers
Inkjet printers are types of printers that recreates digital image by propelling droplets of ink onto
paper, plastic, or other substrate.
In the inkjet printing mechanism, the print head has several tiny nozzles, also called jets. As the
paper moves past the print head, the nozzles spray ink onto it, forming the characters and images.
An inkjet printer can produce from 100 to several hundred pages, depending on the nature of the
hard copy, before the ink cartridges must be replaced. There is usually one black ink cartridge
and one so-called color cartridges containing ink in primary pigments.
They are used for printing greeting cards, banners, business cards, and letterhead, envelopes,
labels, greeting cards.
Cartridge
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A cartridge is physical object in a protective plastic shell that contains a substance (black ink or
powder substances) that is inserted into a printer, allowing it to print. A compatible toner
cartridge is one that is specially designed to work with a particular brand and model of printer.
Photo printers
Photo printers are color printers that produce photo-lab-quality pictures. Some photo printers
print just one or two sizes of images. Others print up to letter size, legal size, or even larger.
Most photo printers are pict Bridge enabled, so that you can print pictures without a computer.
LaserJet printers
LaserJet printers are high-speed and quality nonimpact printer that uses photocopier technology.
When a document is sent to the printer, a laser beam "draws" the document on a selenium-coated
drum using electrical charges. After the drum is charged, it is rolled in toner, a dry black powder
type of ink. The toner adheres to the charged image on the drum. The toner is transferred onto a
piece of paper and fused to the paper with heat and pressure. After the document is printed, the
electrical charge is removed from the drum and the excess toner is collected. Most laser printers
print only in monochrome. A color laser printer is up to 10 times more expensive than a
monochrome laser printer.
Advantages of LaserJet printers
Are generally quiet and fast.
Can produce high quality output on ordinary papers.
Cost per page of toner cartridges is lower for than for other printers.
Disadvantages of LaserJet printers
The initial cost of LaserJet printers can be high.
A label printer
These are small printers that print on an adhesive (sticky) type of materials that can be
placed on a variety of items such as envelopes, packages, DVDs, photographs, file folders,
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and toys. Most label printers also print bar codes. Label printers are different from ordinary
printers because they need to have special feed mechanisms to handle rolled stock, or tear
sheet (fanfold) stock
Plotters
Plotters are output device that is used to produce high quality graphics in a variety of colors.
Plotters are used to create maps, architectural drawings, graphs and charts.
These are sophisticated printers with a pen like print head that can accurately draw straight,
thin and meandering lines. They are used to produce high-quality architectural drawings
such as blueprints, maps, circuit diagrams, posters, and signs.
These printers are usually very costly, and are used in specialized fields such as engineering, and
graphic art. They use ink-jet printer technology, on a much larger scale, to print professional
quality displays. These printers typically can handle paper with widths up to 98 inches.
Advantages of plotters
Plotters can work on very large sheets of paper while maintaining high resolution.
They can print on a wide variety of flat materials including plywood, aluminum, sheet
steel, cardboard, and plastic.
Plotters allow the same pattern to be drawn thousands of times without any image
degradation.
Disadvantages of plotters
Plotters are quite large when compared to a traditional printer.
Plotters are also much more expensive than a traditional printer.
A mobile printer
This is a small, lightweight, battery-powered printer that allows a mobile user to print from
a notebook computer, Tablet PC, PDA, smart phone or other personal mobile device while
traveling. They fit easily in a briefcase alongside a notebook computer. Mobile printers
mainly use ink-jet, thermal, wax-transfer, or dye-sublimation technology.
There are two main approaches to mobile printing. One involves direct communication between
a mobile device and a printer and communication between a mobile device and a computer
connected to a printer.
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Thermal printers
Thermal printers are non-impact printers generate images by pushing heated pins against a
coated heat-sensitive paper. The coating turns black in the areas where it is heated, producing an
image. Basic thermal printers are cheap, but the print quality is low and the images tend to fade
over time. Thermal printing technology is, however, ideal for use in small devices e.g. ATM
receipt printers.
Advantages of Thermal printers
They are inexpensive.
They are nearly noiseless
They consume very little power compared to other printers
They don‘t experience inconveniences like paper jams or blocked nozzles.
They can produce clear and crisp images with very high resolutions.
Disadvantages of Thermal printers
Needs a special temperature sensitive paper which may be expensive.
Over heats during printing.
The papers have limited shelf lives. They are easily damaged by sunlight,
humidity and chemical vapors.
The papers have to be specially prepared before they can be used in printing
Their print heads cannot be serviced or repaired even if a single dot heater fails.
The print speed is so slow because the heads have to be allowed time to cool before
the next printing cycle.
The print heads also have a short life span than for the other printers.
Inkjet printer Photo printer LaserJet printer Label printer
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Plotters Mobile printer Thermal printer Cartridge
DIFFERENCE BETWEEN IMPACT AND NON-IMPACT PRINTERS
Impact Printers Non impact Printers
1. They print characters or images by striking
print hammer or wheel against an inked ribbon.
1. They print characters and images without
striking the papers.
2. Their speed is slower. 2. Their speed is faster.
3. Their printing quality is lower. 3. Their printing quality is higher.
4. They normally uses continuous paper sheet. 4. They normally uses individual paper sheet.
5. They generate lot noise during printing. 5. They generate no noise during printing.
6. They use inked ribbon for printing. 6. They use toner or cartridge for painting.
7. They are less expensive. 7. They more expensive.
8.Print heads are reliable, durable i.e. can last
for a long time
8.Print heads are less durable
9.They print limited colors 9.They are capable of printing strong clear
colors
10.They are not commonly used today 10.They are commonly used today
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The difference between screen output and print output
Screen output Print output
Displays soft copy output Prints hard copy output
The output is temporarily incase power goes
off
The output is permanent i.e. It can be
maintained for future reference
The output is silent Produces a lot of noise when outputting
especially impact printers
Different styles of print e.g. italics, and color
displays possible.
A styled print is only possible with the
advanced models having the color capabilities.
It is very fast Comparatively slow
Factors to consider when selecting/ buying a printer
1. The initial price and the subsequent coast of maintenance
2. The coast of consumable items like paper quality, cartridges it uses, ribbons etc.
3. Volume of printing expected that helps on the selection of the printer speed range of the
computer.
4. The nature of report and print quality the printer can offer.
5. Range of viability for selected printer like multiple copy facility, print styles, page width
etc.
6. The type of the manufacturer should also be considered.
Speakers
Speakers are output hardware devices that connects to a computer to generate sound. The signal
used to produce the sound that comes from a computer speaker is created by the computer's
sound card.
They receive audio input from the computer's sound card and produce audio output in the form
of sound waves. Most computer speakers are active speakers, meaning they have an internal
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amplifier which allows you to increase the volume, or amplitude, of the sound. Speakers usually
come in pairs, which allow them to produce stereo sound from two separate audio channels.
Most personal computers have a small internal speaker that usually outputs only low-quality
sound. For this reason, many personal computer users add speaker systems to their computers to
generate a higher-quality sound for playing games, interacting with multimedia presentations,
listening to music, and viewing movies.
Headsets
Headsets are hardware devices that connect to a telephone or computer that allow the user to talk
and listen while keeping their hands free. Headsets are commonly used in technical support and
customer service centers which allow the employee to talk to a customer while typing
information into a computer.
Ear phones /Headphones;
Earphone is an electrical device worn on the ear to receive radio or
telephone communications or to listen to a radio, MP3 player, etc.
They are used on the web to listen to interviews, talk shows, sporting events, news, recorded
music, and live concerts from many radio and television stations.
These are used in a computer laboratory or other crowded environments, where speakers might
not be practical. They are normally connected in a port on the sound card, in a speaker, or on the
front of the system unit. With the headphone or earphone, only the individual wearing the
headset hears the sound from the computer
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Fax (or facsimile) machine
A fax machine is a device that transmits and receives typed or hand written documents over
telephone lines. A stand alone fax machine scans the original document, converts the image into
digitized data, and transmits the digitized image. A fax machine at the receiving end reads the
incoming data, converts the digitized data into an image, and prints or stores a copy of the
original image.
Fax capability also can be added to a computer using an external fax modem.
Multifunction peripheral (MFP)
A multifunction peripheral (MFP) is a single device that performs a variety of functions
such as printing, copying and scanning that would otherwise be carried out by separate
peripheral devices. This looks like a copy machine but provides the functionality of a
printer, scanner, copy machine, and perhaps a fax machine.
Data projectors
A data projector is an output device that can take images generated by a computer and
reproduce them onto a screen, wall, or other surface so that an audience of people can see the
image clearly. For example, you could use a projector to show a presentation on a large screen
so that everyone in the room can see it.
There are three types of data projectors;
A liquid crystal display (LCD) projector
A digital light processing (DLP) projector
Cathode ray Tube projector
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Applications of data projector today
Project a PowerPoint presentation at a business meeting.
Project a computer screen to teach a class in school.
Project a TV or computer with a movie playing to a large screen.
Demonstrate a product or service at a convention center.
Transform a wall, house, or other object to give it a different appearance.
Interactive whiteboard (IWB)
Interactive whiteboard also known as smart board is an instructional tool that allows computer
images to be displayed onto a board using a digital projector. The instructor can then manipulate
the elements on the board by using his finger as a mouse, directly on the screen. Items can be
dragged, clicked and copied and the lecturer can handwrite notes, which can be transformed into
text and saved.
Terminal output devices
Are electronic or electromechanical hardware device that are used for entering data into, and
displaying or printing data from, a computer or a computing system.
Spectacles
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These are common in modern computer games especially on fights. The user wears the glasses
like ordinary sun glasses except that here, instead of seeing through the glasses, one will be
treated with high quality three – dimensional pictures. It is similar to being in a cinema hall.
COMMUNICATION DEVICES
Communication devices are devices that connects the communications channel to a sending
device by converting the data, instruction or information from the sending device into signals
that can be carried by a communications channel
Example of communication devices;
Modem
Router
Hub
Switch
Gateway
Cables
Bridge
Repeater
Network interface card
Multiplexer
Modem
A modem is a communication device that converts between analog and digital signals
Router
Router is an intelligent communications device that sends communications traffic to the
appropriate network using the fastest available path
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Hub/concentrator
A hub is a communication device that connects multiple devices to the network. Its function is to
send and receive signals along the network between the devices connected to it by broadcasting
the data to all the devices/computers. It serves as a central meeting place for cables from
computers, servers and peripherals on the network.
Switch
A switch is a high-speed device that maintains a bridging table, keeping track of which hardware
addresses are located on which network segment. It maps the internet protocol (IP) address with
the Media Access Control (MAC) address of the LAN card.
Gateway
A gateway is a communication device that consist of a combination of hardware and software
that connects networks that use different protocol technologies by performing the required
protocol conversions
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Cables
Cables are also known as cords, connectors or plugs refers to one or more wires covered in a
plastic covering that allows for the transmission of power or data between devices.
They are insulated wires having a protective casing and used for transmitting electricity or
telecommunication signals.
There are two main types of computer cables;
Data cables are cables that provide communication between devices. Power cables are any
cables that powers the devices
Bridge
A bridge is a communication device that links two local area networks that use the same address
method or protocol. It accepts all packets from each network addressed to devices on the other,
buffers them, and retransmits them to the other network.
Repeaters
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A repeater is a communication device that accepts a signal from a transmission medium,
amplifies it, and retransmits it over the medium in order to overcome attenuation.
N.B Attenuation is the process by which signals undergo reduction in its strength as it
travels over long distances.
Network interface cards (NIC) or LAN Adapter
A network interface card is an electronic communication device or an expansion card that
enables and other devices a computer to connect to a network.
Multiplexer
Multiplexer is a communications device that combines two or more input signals from various
devices into a single stream of data and then transmits it over a single transmission medium.
TOPIC 3: COMPUTER SOFTWARE:
Computer software is a program that consists of step by step instructions that tell the computer
how to perform a given task. Software consists of computer programs that control the working of
the computer hardware.
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A program; A computer program is a sequence of instructions, written to perform a specified
task with a computer. Without software, the computer hardware cannot do anything.
Characteristics of computer software
Computer software is intangible
Computer software gives instructions/procedures to computers
Computer software is copy righted
Computer software can be installed
Computer software is executable
computer software is loaded into Memory when running
All software has a source Code written by a programming Language.
What the software consumer wants
Cheap to buy
Easy to learn
Easy to use
Solves the problem
Reliable
Powerful
Fast
Flexible
Available (easy to obtain
What the software producer wants:
Cheap to produce
Well-defined behaviour
Easy to "sell"
Easy to maintain
Reliable
Easy to use
Flexible
Quick to produce
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Factors to consider before obtaining a software program
Correctness: does the software do what it is supposed to do (according to the design specs)?
Robustness: how does the software respond to unexpected conditions (wrong input)?
User-friendliness: is the software easy to use by users from the intended audience?
Adaptability: how difficult is it to modify the software to adjust to an ever-changing world?
Reusability: can parts of the software be easily reused to build other software systems?
Interoperability: does the software interface with other software systems?
Efficiency: does the software make good use of its resources (memory, disk, CPU, network)?
Portability: can the software to easily ported (moved) to other operating
Security: does the software protect the information it is responsible for?
Categories of computer software
Computer software is categorized into two groups;
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System software
Application software
Systems software
These are a set of instructions that control the operation of the computer and its devices. It refers
to the various computer programs that control the way a computer operates. It is a collection of
software found in the CPU, and inside ROM (firmware).
Firmware is a small program recorded by the computer manufacturers at the factory on
electronic chips mounted on the computer’s motherboard or any other devices to control the
devices. Examples of devices that contain firmware include remote control, cell phones,
digital cameras and ROM chips.
Characteristics of system software
It is machine dependent.
It serves as the interface between the users.
They are written by computer programmers or professional system programmers.
Some system software resides in ROM (permanently) hence known as firm ware.
It is usually supplied by the manufacturers of the computer
Types of system software
Operating system
Utility software
Programming languages
Operating system;
Operating system is a set of programs that coordinate the operation of all hardware devices and
application software components of a computer. The operating system relies on device drivers to
communicate with each device in the computer.
A device driver is a program that controls a particular type of device that is attached to a
computer by converting the general input/output instructions of the operating system to messages
that a device type can understand. It is small program that tells the operating system how to
communicate with a device
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Examples of operating system
Disk Operating System (DOS): It is the main system control program that enables the computer
to operate.
Windows Operating System: These are operating systems that use icon – based graphical user
interface that simplifies working on a computer such as Windows95, Windows98, windows 10,
windows 8.1, windows 7 etc.
Networking Operating Systems (NOS): These are system software’s that organize and
coordinates the activities on a local area network. They are designed to be used on several
computers that exist on a network. They include; Sun Solaris, UNIX, Linux, Novell Netware etc.
Tasks that are perform by networking operating system
Administration of network users
System maintenance tasks such as backup
File management tasks
Prioritizing print jobs on the network
Monitoring security on network resources
Palm operating system: Is an operating system designed for the hand – held computers
(Personal Digital Assistants– PDAs). An example of palm operating system is Pocket PC2002.
Ubuntu is a free and open source operating system and Linux distribution freely available with
both community and professional support. Ubuntu is offered in three official editions; Ubuntu
Desktop for personal computers, Ubuntu Server for servers and the cloud, and Ubuntu
Core for internet devices.
Functions of the Operating System
Controls the hardware resources like accessing disk drives, printers and keyboard
It calls into memory programs and instructions when required
It protect hardware, software and data from improper use e.g. when deleting a file.
It provides error correcting routines for instance when data is lost during transfer.
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It helps in managing files and memory by allocating items to the area of memory while
they are being processed.
It Schedules and loads other programs in order to provide a continuous sequence of
operation.
It enable application software to interface with the hardware
Provides an interface between the user and the application software and the hardware
It monitors system performance by accessing and reporting information about various
system resources and other devices.
Classification of operating system
Operating systems are categorized based on the followings:
1) The number of tasks an operating system can perform concurrently
2) According to the number of users that can be logged in at a time
3) The human computer interface (HCI) used.
4) According to the processing mode
Classification according to tasks handled
Single operating system
Multitasking operating system
Multithreading operating system
Multiprocessing operating system
Multi programming operating system
Single task operating system is a type of operating system that allows processing of only one
user program at a time. This implies that the user can only run one interactive program at a time.
Multitasking operating system is a type of operating system capable of allowing multiple
software processes to run at the same time on one computer (CPU).
Multithreading operating systems is a type of operating system that allows different parts of a
software program to run concurrently. Multi threading is the ability of a program to manage its
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use by more than one user at a time and to manage multiple requests by the same user without
having multiple copies of the program running on the computer.
Multi processing operating system is a type of operating system capable of supporting and using
more than one computer processor at a time
Multi programming operating system is a type of operating system cable of executing two or
more programs on a multi user operating system.
Classification according to the number of users
Single user operating system is a type of operating system designed to manage the computer so
that a single user can effectively do one task at a time. The Palm OS for Palm handheld
computers is a good example of a modern single-user, single-task operating system.
Multiuser operating system is a type of operating system that allows multiple users to use the
same computer at the same time.
Classification of OS according to human–computer interface
The user interface is the aggregate of means by which the user interacts with the computer
system. A user interface provides:
Input, allowing the users to manipulate a system
Output, allowing the system to indicate the effects of the users' manipulation
Types of computer user interface
Graphical user interface
Command line interface
Touch user interface
Voice recognition interface
Graphical user interface (GUI) operating systems
A graphical user interface (GUI) is a type of user interface that allows users to interact with
programs by manipulating graphics, along with a keyboard and pointing devices such as a
mouse, to provide an easy-to-use interface to a program.
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Advantages of a GUI operating System
They make computer operation more intuitive, and thus easier to learn and use.
GUIs generally provide users with immediate, visual feedback about the effect of each
action. For example, when a user deletes an icon representing a file, the icon immediately
disappears, confirming that the file has been deleted.
GUIs allow users to take full advantage of the powerful multitasking capabilities of
modern operating systems by allowing such multiple programs to be displayed
simultaneously.
GUIs have windows that enable a user easily to view, control, and manipulate multiple
things at once.
GUI is easy to use because of the use of graphics because user simply uses the mouse to
choose the appropriate icons/commands.
GUI enables a user to create shortcuts, tasks, or other similar actions to complete a task or
run a program
Disadvantages of GUI operating System
GUI requires a lot of system resources (e.g. memory space) because of each of the
elements that need to be loaded such as icons, fonts, etc.
When it is not properly built, it can be very difficult to work with.
It requires the installation of additional software, e.g., the "runtime environment" in the
case of java.
It is very slow to download into memory.
The user choices are restricted to those on the menus
Command-line user interface (CLI) operating system
The command line is a user interface (CLI) that is navigated by typing commands at a command
prompt; for example, the root MS-DOS command line prompt generally is C:\>.CLI can only be
navigated by using a keyboard and entering commands; it does not use a mouse.
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This method of instructing a computer to perform a given task is referred to as ‘entering’ a
command: the system waits for the user to conclude the submitting of the text command by
pressing the Enter key on the keyboard.
Advantages of command-line user interface
It does not require a lot of memory resources to run because it is light.
Users have much more control of their file system and operating system in a command
line interface. For example, users can easily copy a specific file from one location to
another with a one-line command.
It is precise because the user states exactly what he or she wants to do, and the more
sophisticated CLIs keep a record of the commands that have been issued.
Disadvantages of command-line user interface
Difficult to use by new users because of the memorization and familiarity of commands
needed to operate a command line interface new user find it much more difficult to
successfully navigate and operate a command line interface.
CLIs cannot show images.
It is fast and precise because command line users only need to use their keyboards to
navigate a command line interface and often only need to execute a few lines to perform
a task.
Difference between command Line Interface and Graphic User interface
CLI GUI
The user has to know the commands or look
them up
The commands are much more intuitive
The commands usually have to be entered in
full
Command shortcuts are possible such as
<Ctrl> C to copy
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The user has to learn the commands and more
training is needed
Less learning and training by the user is
required
The interface can be daunting, more difficult
to use and the user is more likely to make
mistakes
The GUI is more user-friendly
There are no graphics Graphics are used to represent tasks, files etc.
There are no menus Menus are used for making choices and
selections
The user has complete control The user choices are restricted to those on the
menus
Commands have to be entered accurately with
the correct spellings and syntax (rules)
Spelling and typing errors are avoided
No pointing device is used A pointing device is used to select items and
make choices
Touch user interface
These are graphical user interface that uses a touch screen display as a combined input and
output device
Voice user interfaces
These are types of user interfaces that accept input and provide output by generating a voice
prompt by pressing keys or buttons or responding verbally to the interface.
Classification of operating System according to processing mode
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Processing mode refers to the method of processing that the operating system supports.
Examples include;
Time operating system
Batch process operating system
Real-time operating system
Distributed operating system
Embedded operating system
Time sharing operating system is method where multiple users with different programs interact
at the same time on a multi-access system. For example in a learning institution where students
and professors are connected to the central CPU at one time from different terminals
Batch process operating system is where programs and data are collected together in a batch
queue before processing starts. Batch processing can be used for fairly automatic tasks; for
example, weekly or monthly payroll processing, processing utility bills (water, electricity, etc.)
and credit card bills.
Real-time processing operating systems are the type of operating system designed to respond
to an event within a predetermined time. As soon as the data is input, it is processed and output
immediately. These types of operating systems are found in environments where computers are
responsible for controlling systems continuously; for example, robotics, manufacturing,
interactive games, airlines and theatre booking systems.
Distributed operating systems are types of operating systems that manage a group of
distributed computers. Distributed computations are carried out on computer networks that work
in cooperation.
Embedded operating systems are types of operating systems designed to operate on small
machines like PDAs. They are able to operate with a limited number of resources.
Factors to consider when choosing an operating system
The Human–computer interface
The Applications intended for the computer.
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The availability of operating system on the market.
The basic design of the computer.
The Hardware provisions of the computer.
The available of operating systems for all sizes of computers.
The operating system should be user friendly.
The cost of the operating system
Reliability and security provided by the operating system.
The number of processors and hardware devices it can support.
The number of users it can support
The availability of basic utilities and accessory programs within the operating system
Installation and un-installation of operating system
There are many reasons why you might need to install or reinstall an operating system:
When you need to upgrade to a more advanced operating system.
When the existing operating system files have been corrupted and it therefore no longer
functions.
When you need to set up a brand new machine which was supplied without an operating
system.
When you need to perform a recovery on your computer after it has suffered a fatal error
(accidental error)
In case of an irreparable Registry or System file corruption in the existing Windows
installation.
Note: Before doing a clean install of an operating system, you will need to back up your data
files.
Utility programs
A utility program is a type of system software that allows a user to perform maintenance-type
tasks, usually related to managing a computer, its programs and its devices.
Utility programs included with most operating systems provide the following functions:
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Managing and searching for files,
Viewing images,
Securing a computer from unauthorized access,
Uninstalling programs,
Scanning disks,
Defragmenting disks,
Diagnosing problems,
Backing up files and disks,
Setting up screen savers.etc
Examples of utility program include;
A file manager;
It is a utility that performs functions related to file and disk management such as;
Formatting and copying disks
Organizing files in folders
Displaying a list of files on a storage medium
Checking the amount of used or free space on a storage medium
Organizing, copying, renaming, deleting, moving, and sorting files; and
Creating shortcuts.
A shortcut is an icon on the desktop that provides a user with immediate access to a program or
file.
Formatting a disk is the process of preparing a disk for reading and writing.
A search utility
A search utility is a program that attempts to locate a file on your computer based on the criteria
you specify. The criteria could be a word or words contained in a file, date the file was created or
modified, size of the file, location of the file, file name, and other similar properties.
A personal firewall
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A personal firewall is a utility that detects and protects a personal computer from unauthorized
intrusions. Personal firewalls constantly monitor all transmissions to and from a computer. When
connected to the Internet, your computer is vulnerable to attacks from hackers (people who try to
access a computer or network illegally).
An uninstaller
An uninstaller is a utility that removes a program, as well as any associated entries in the system
files.
A disk scanner
A disk scanner is a utility that searches for and removes unnecessary files from the hard disk. It
is used to detect and correct both physical and logical problems on a hard disk or floppy disk and
searches for and removes the unwanted files. A physical problem is one with the media e.g. any
scratch on the surface of the disk.
A disk defragmenter
A disk defragmenter is a utility that reorganizes the files and unused space on a computer's hard
disk so that operating system can be able to access data quickly and running of programs faster.
Disk defragmentation enables data to be accessed more quickly and programs to be run faster.
NB; Defragmentation is the process of reorganizing the disk so that the files are stored in
contiguous sectors meanwhile Fragmentation on the other hand is the process of in which files
are divided into pieces scattered around the disk. Fragmentation occurs naturally when you use
a disk frequently, creating, deleting, and modifying files. At some point, the operating system
needs to store parts of a file in noncontiguous clusters.
A diagnostic utility
A diagnostic utility is a type of utility that compiles technical information about your computer's
hardware and certain system software programs and then prepares a report outlining any
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identified problems.
A backup utility
A backup utility is a utility that allow users to copy, or back up, selected files or an entire hard
disk to another storage medium. During the backup process, the backup utility monitors progress
and alerts you if it needs additional media, such as another CD or tape.
Disk checker
Disk checker is a utility that scan the contents of a hard disk to find files or areas that are faulty.
Disk cleaner
Disk cleaner is a utility used to find files that are unnecessary to computer and can decide to
delete.
Disk compression
Disk compression is a type of utility used transparently to compress / uncompress the contents of
a disk, and increasing the capacity of the disk.
Network utility
Network utility is a utility used to analyze the computer's network connectivity, configure
network settings, check data transfer or log events.
A screen saver
A screen saver is a utility that causes a display device's screen to show a moving image or blank
screen if no keyboard or mouse activity occurs for a specified time. When you press a key on the
keyboard or move the mouse, the screensaver disappears and the screen returns to the previous
state.
Importance of a screen saver
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To prevent ghosting problem that is images that are permanently etched on a monitor’s
screen
It prevents unwanted lookers from accessing information or data from your computer.
For advertising business on the screen
For entertainment- in which digital photos can be put on your screen as moving pictures
Debugger
Debugger is a utility program used during the testing of a program by tracing and removing of
errors from newly installed programs.
N.B. Debugging is a process of removing of errors from installed programs in the computer
system.
Antivirus utility
Antivirus utility is a utility used to detect remove, and prevent viruses from a computer‘s
memory or storage devices.
A file compression utility
A file compression utility is a type of utility used to reduce or shrink the size of a file. A
compressed file takes up less storage space on a hard disk than the original file. Compressing
files frees up room on the storage media and improves system performance.
Disk partition
Disk partition is a utility used to divide an individual drive into multiple logical drives, each with
its own file system which can be mounted by the operating system and treated as an individual
drive.
Programming languages
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A computer program is a step by step set of instructions that a computer has to work through in
a logical sequence in order to carry out a particular task. The computer executes these
instructions when told to do so by the user.
Computer programming
Computer Programming is defined as the process of creating computer software using a
programming Language. Computer programs are written by Human individuals (Programmers).
Programming Languages
Programming languages are the vocabulary and set of grammatical rules for instructing a
computer to perform specific tasks. There are many different types of programming languages
each having a unique set of keywords (words that it understands) and a special syntax
(grammar) for organizing program instructions.
It is a set of instructions used to direct the operation of a computer.
Characteristics of programming languages
Every programming language has instructions for input and output.
They have instructions for calculations.
They have instructions for transfer of control instructions for data storage and retrieval
They gave instructions for data movements
Classification of programming languages
1. Machine code languages (First generation language)
2. Assembly languages (second generation language)
3. High level languages (Third generation language)
4. Fourth generation languages
5. Fifth generation languages
Categories of programming languages
There are two categories of programming languages;
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Low Level Languages
High Level Languages
Low Level Languages
Low level languages are languages written without sequence of text including words, numbers,
and punctuations.
There are two types of low level languages;
Machine Code (First generation Language or1GL)
Assembly language (Second generation Language or 2GL)
Machine Code languages (First generation Language or1GL)
These are languages written in binary form represented in the binary system by 1 and 0
respectively. Machine language codes are very difficult to read and write by human beings hence
susceptible to errors.
Characteristics of machine code languages (First Generation Language)
They are fast to execute because it is already in the language that the computer can
understand.
Difficult to interpret hence requires the aid of a reference manual to interpret the
meaning of each code).
Very easy to make mistakes in the sequence of 1s and 0s; replacing a 1 for a 0 can result
in the wrong command/instruction being executed
It is difficult to identify mistakes made
Time-consuming and tedious to write
They are machine dependent
Programming becomes more difficult as the complexity of the program increases
Advantages of machine code languages
They are efficient
They allow control of each operation
They don’t require either a compiler or interpreter
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Disadvantages of machine code languages
They are very difficult to learn and very unfamiliar to humans.
They are not user-friendly
Their programs cannot be use in a different machine because of different codes.
It is very tiresome to program in machine code language and many errors are likely to
occur.
It is difficult to identify mistakes made
Time-consuming and tedious to write
Assembly language (Second generation Language or2GL)
These are low level languages that consist of Mnemonics symbols (English like words) used to
represent the binary digits of zeros and ones of machine code language. An assembly language
program has to be translated into machine language by an assembler for a computer to
understand.
Characteristics of Assembly languages (Second Generation Language (2GL)
Similar to machine language, assembly languages are machine dependent.
Assembly languages are faster and more efficient in the use of hardware than high-level
programming languages.
Assembly languages have to be translated into machine language by language translators
known as assemblers for the processor to understand.
They are easier to be written than machine language
The code is not very easy to understand, hence the introduction of high level
programming languages.
Advantages of assembly languages
Programs are written more easily compare to machine language.
They had closer control over the computer hardware and executes very efficiently.
They are useful for writing operating systems and game programs which require fast and
efficient CPU.
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Disadvantages of assembly language
They are designed for specific machines and specific processors.
Programming in these languages is tiresome because programs cannot be moved from
one computer architecture to another without re – writing the code.
Assembly codes needs translation to be executed by the computer.
Programmers are trained in learning and writing programs.
High Level Languages (Third generation Languages or3GLs)
High level languages are languages which consist of statements that resemble human language or
mathematical notations such as valid words, symbols and sentences
Characteristics of high-level languages
They are machine independent hence portable
They are user friendly and easy to learn
High-level language programs are easy to debug
They are more flexible hence they enhance the creativity of the programmer, increasing
productivity
They are executed much slower than low-level programming languages
They have to be translated into machine code before execution; this is done by compilers
and Assemblers.
One instruction translates into several machine code instructions
Advantages of high level languages
They are easy to learn because they use English like vocabularies
They are much easier to learn, understand, write, correct and revise compared to machine
language
They are machine independent and user friendly.
Programs are easy to modify correct errors and maintain
Disadvantages of high level languages
A source program needs a compiler/translator to converts it into machine code.
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They take a lot of time because they consume large amount of memory.
They are less efficient in the use of CPU and other facilities.
Qualities if a good programming language
Suitability of the problem Clarity and simplicity Efficiency Availability Consistency
Categories of high level languages
i) Commercial languages
ii) Scientific languages
iii) Special purpose languages
iv) Multipurpose languages
v) Command languages for operating system
Commercial languages
This language was developed purposely for commercial use. Example of commercial language is
COBOL
It is an acronym for Common Ordinary Business Oriented Language. It was a high level
language widely used in business. COBOL has the ability to handle input and output of large
volumes of alphanumeric data.
Advantages of COBOL
It is fair and easy to understand.
It can be used on different types of computers.
It enables programmers to easily re – arrange records within a file.
It enables programmers to easily produce reports.
Disadvantages of COBOL
Coding is lengthy and tiresome to make.
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It takes longer to learn
Scientific languages
These languages were developed purposely for engineering applications and for scientific use.
Examples include; FORTRAN (Formula Translation), and ALGOL (Algorithmic Language)
FORTRAN (Formula Translation)
It was developed in 1956 by IBM to provide an easier way of writing scientific and engineering
applications because of its simplicity, conciseness, standardization, efficiency and numerical
precision.
Advantages of FORTRAN
It is widely accepted and understood.
It is easy to write a simple FORTRAN program.
It has mathematical functions that are good for problems solving.
Disadvantages of FORTRAN
It is difficult to use in other applications other than scientific and engineering
applications.
It is not easy to accomplished input and output operations.
It is difficult to read reports and screen display.
ALGOL (Algorithmic Language). It is suitable for scientific and engineering computations.
Special purpose languages
These are languages intended to be tailor made for a particular type of problem, e.g. machine
control, wages, simulations, control experiments. Examples are; Ada and SQL (structure Query
language).
Multipurpose languages
These are languages which are intended to deal with a number of different types of application
areas especially in the areas of business and science, e.g. BASIC, Pascal, C, C++, and JAVA
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BASIC (Beginners All Purpose Symbolic Instruction Code)
It was developed in 1964 to teach programming languages to beginners who did not have any
knowledge in programming. It is a simple language which is easy to learn and to use it.
Advantages of BASIC
It is easy to learn and use.
It is so popular
Several books exist that are used as self – teaching manuals.
Disadvantages of BASIC
It is not a standard language
There are many different versions of BASIC with so little compatibility between them.
PASCAL
It was named in remembrance of the inventor of the mechanical adding calculator, Pascal Blaise.
It was developed purposely to teach the concepts of structured programming.
Advantages of Pascal
It reinforces the principles of structured programming.
It is not limited to business or scientific applications.
C
It is a high level language. It is the most portable general purpose language. Derivatives of C are;
C+.
C++ the language is based on C and it is very popular for object oriented programming (OOP)
JAVA is an Object Oriented Programming (OOP) language that resembles a simplified form of
C++. Object Oriented Programming (OOP) uses objects which combine data and behavior. OOP
enables rapid program development. Examples include; Visual Basic.
Fourth generation Languages (4GLs / Application generators / program generators)
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These are languages designed to make the process of creating a computer – based application
easier by doing the programming themselves. The user defines certain tasks and then the
application generators will create the program code that will perform the tasks that have been
defined. Examples of 4GLs
Structured Query Language
Fifth Generation Languages /5GLs (Artificial Intelligence Languages)
These are languages used in intelligent knowledge based systems (IKBs) such as robots.
They―think and reason like human beings because of the programs installed on them. They are
extremely used in artificial intelligence projects like space exploration.
Web development languages
These include HTML and JAVA. HTML (Hypertext Markup Language) is one of the
programming languages used to create web pages for the internet and intranets.
Factors to consider when choosing a good programming language
Suitability of the problem. Clarity and simplicity. Efficiency Availability Consistency
Language processors (translators)
These are programs used to translate high level programming languages to low level languages
that processors can understand.
Compilers
These translate a program written in a high level language into machine code language. The
entire program is translated into machine code at once.
Assemblers
These translate a low level language (assembly language) into machine code.
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Interpreters
These translate source program, line by line while the program is running. This is done each time
a program is executed. As a result, a program running under an interpreter runs very slowly
compared to a compiled program.
Linkers
These are programs used to combine compiled programs and determine where the program will
be located in the memory.
APPLICATION SOFTWARE
Application software’s are programs that perform specific tasks for users. They are programs
designed to enable a computer to do a particular job.
Categories of application software
General-purpose software
This is software that is not written for any specific business or organization but which can be
used or adapted to suit a wide selection of users’ specific needs. For example, a teacher can use a
spreadsheet package to prepare a student end of term grades report, and a word processor to
write letters to parents, but the same packages could be used in business to perform different
tasks such as accounting or memo writing.
Specialized software
Specialized software is a program written for a specific task rather than for a broad application
area. These programs provide facilities specifically for the purpose for which they were
designed. For example, a payroll program will usually only be able to deal with all aspects of a
company’s payroll only, it cannot be used for other purposes such as word processing, or
drawing. Other examples of specialized software are expert systems, accounting programs and
theatre or airline booking programs.
Open source software (OSS)
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Open source software is copyrighted software for which the software plus the source code are
freely distributed.
The OSS free software license/copyright permits users to use, change, and improve the software,
and to redistribute it in modified or unmodified forms. It is very often developed in a public,
collaborative manner.
Source codes (code) are the program instructions written in a computer programming language
to specify the actions to be performed by a computer.
A software license (copyright) is a legal instrument governing the usage or redistribution of
software to protect the interests of the program designer for example, software license may grant
an end-user permission to use one or more copies of software in ways where such a use does not
constitute copyright infringement of the software owner’s exclusive rights under copyright law.
In addition to granting rights and imposing restrictions on the use of software, a software license
contains provisions which allocate liability and responsibility between the parties entering into
the license agreement.
Freeware
Freeware is copyrighted software that is offered at no cost but whose source code is not
provided. Software that is not freeware is referred to as commercial software or pay ware or
commercial software.
Proprietary software (closed source software)
Proprietary software is copyrighted software obtained at a cost where the software publisher
grants a license to use one or more copies of the software, but the ownership of those copies
remains with the software publisher such that all rights regarding the software are reserved by
the software publisher.
Shareware
Shareware is copyrighted software that is distributed free on a trial basis (as a trial version) with
the understanding that the user may need or want to pay for it later.
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Shareware developers offer the trial version of their program with a built-in expiration date, say
15, 30 or 60 days, as an enticement to buy the complete version of the program. Once the trial
period has passed, the program may stop running until a license is purchased.
Public domain software
Public domain software is the software which is not copyrighted because it has been formally
released to the public domain such that there is no copyright restriction on it.
Copy righted software
This is free software whose distribution terms ensure that all copies of all/modified versions of
the copyrighted software to carry the same distribution terms like the original version.
Software Piracy
Software Piracy is the unauthorized/illegal duplication and use of computer software/programs.
Integrated software
Integrated software is a single application package which combines the most commonly used
functions and commands or interface of many productivity software programs such as word
processor, spreadsheet, database, and communication and graphics presentation packages. For
example, most word processors such as Microsoft office have the capability of mailing, creating
web pages, drawing, charting, and others in addition to word processing.
Software suites
A software suite, also known as application suite or productivity suite, is a software package that
has several applications that work well together because they have related functions, features and
user interfaces, and are able to interact with each other.
Business applications often come in suites, e.g. Microsoft Office, OpenOffice.org, and iWork,
which bundle together a word processor application, a spreadsheet application, presentation
graphics, database and e-mail applications, etc.
Advantages of integrated software and software suites
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It is easy to transfer data from one component of the application to another.
Integrated software takes up less disk space than individual packages.
The user can move much faster from one application to the next.
It is usually easier to learn how to use the applications in a software suite because the
user interface for choosing commands is similar for all applications.
A software suite tends to be more powerful and versatile than individual applications.
A software suite is less likely to crash and contains fewer errors (bugs), since it has been
widely tried and tested.
The producers of software suites often offer after-sales services (e.g. online help
facilities); users can also get support from user groups and magazines.
Software suites are usually cheaper to buy than purchasing the packages individually.
Disadvantages of integrated software and software suites
Not all the features of a single application are included.
Some integrated packages do not contain all the applications that may be required to
complete a task.
Classifications of application software
Application software’s are classified into two;
Special purpose/Custom (Tailor –made software)
General purpose/Off-the shelf software (standard software)
Special purpose/custom (tailor-made) software
Custom-made software is a program uniquely designed based on the user’s request to perform
particular user’s needs. It is designed to perform a specific group of tasks as requested by the
user that may differ from those done by other already available software.
The individual user hires programmers to design such a program which does not target the
general market and therefore is not available for sale to the general public.
Examples of custom made software
Locally made school management information systems (SMIS)
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Inventory management systems
Payroll management systems
Library management systems
Advantages of Custom-made software
A custom-made application directly addresses the user’s needs because it is written to the
user’s requirements and fits in with his/her work.
The solutions it offers given the greatest depth, breadth and flexibility possible in meeting
the needs of an organization, since the software product is tailored to the organization’s
specifications.
The software developer delivers and installs the software and trains the end users in the
use of the new software.
The software also performs tasks that the general purpose software cannot perform.
This kind of software can be quickly changed when the needs of the organization change,
since the source code belongs to the company.
Disadvantages of custom made software
High costs of developing the software, on-site installation, support and training.
It takes time to acquire because of the need to get information necessary and to write the
code of the new software.
There is high possibility of undetected errors/bugs in the software.
Off-the-shelf software (OTS) or standard software
These are commercial software packages that are already-made and available for sale, lease, or
license to users and copyrighted, designed to meet the needs of a wide variety of users.
Most software developing companies such as Microsoft Corporation design package and make
available their software package for purchase on the software market for users to make a choice
to buy the software if they think it meets their needs.
Examples of off-shelf software packages
MS office suite
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Computer game packages
Education software packages
Advantages of off-the-shelf software
Off-the-shelf software’s are relatively cheap. The cost of development can be spread over
a large number of users.
Off-the-shelf software offers a wide range of capabilities, perform several functions.
They are easily available from most computer vendors
This software is thoroughly tested so there are no serious problems or bugs.
Off-shelf has a lot of user support that is; books, user guides, online help and discussion
forums on the Internet.
Off-shelf is easy to learn and use (user friendly)
Off-shelf can be customized to the user’s needs.
The off the shelf programs are easy to install.
Disadvantages of off-the-shelf software:
Off-the-shelf software is highly complex because it includes large sections that a user
may never use.
Off-the-shelf software does not address needs of specific users.
Off-the-shelf software may take a long time to learn properly. This is because this
software tends to be large and complicated.
Using off-shelf is time consuming to learn and adopt because it requires the user to adapt
to the system itself to do the work.
It is very difficult to gain any competitive advantage from its use over business rivals
because they use the same software.
Examples of application software
Word processing software
Spreadsheet software
Database software
Presentation software
Desktop publishing software
Accounting software
Paint and image editing software
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Web page authoring software
Video and audio editing software
Educational software
Entertainment software
Communication software etc
Uses of application software
There are many different applications programs:
Word-processor: allows you to create, edit, store and print a range of different text documents;
from letters and faxes to books and essays.
Spreadsheet: enables you to use formulas to perform a large number of calculations on data
stored in cells arranged in rows and columns. You can investigate a mathematical problem,
create a budget plan to forecast how much you can save in a year or model the results of a
science experiment and draw a chart of your results.
Database: uses forms to store data in tables made up of records and fields. The data can be
searched using queries in order to find out useful information. It can be used to create anything
from an address book to a complex application that produces end of year reports.
Graphics program: can be used to create posters, perform image processing in order to improve
or alter photographs or create original artwork.
DTP software: Desk Top Publishing software allows you to manipulate text and graphics in
frames on a page in order to create magazines, brochures and other complex documents.
Presentation Software: allows you to create a slideshow to illustrate a talk, or a presentation for
other people to investigate as a kiosk application.
Communication software: could include a web browser or email client software as well as
other programs that allow you to communicate with
Difference between an app and an application
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An app is a piece of software designed for a single purpose or a single function meanwhile an
application is a piece of software that performs a variety of related functions. Typically, if an app
breaks, life goes on, while applications are considered critical to normal business function and
are therefore considered to be of higher value.
APPLICATION PROGRAMS
These are programs that are designed to perform specific tasks for the user. These are programs
that do the real work for the user. Examples include:-
Word processing
Spread sheets
Presentation
Databases
Graphic design
Desktop publishing
TOPIC 4: WORD PROCESSING
Word processing is the process of creating text based documents such as reports, letters,
brochures, memos, mailing labels and newsletters using word processor.
Word processor is software used to create, edit, format, save and print text based documents.
Examples of word processing software include;
Microsoft word
Corel WordPerfect
Lotus WordPro
WordPad
WordStar
Abi word.
Mac write
Ami pro.
Magic wand. e.t.c
Functions of word processing software
Allow text to be edited easily e.g. insert, delete and move text anywhere in the current
document
It can be used in mailing documents
It is use for mail merging letters.
It can be used in graphics creating and handling e.g. frames, shapes
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It has inbuilt mathematical formulae especially in tables which can be used in
manipulating data easily.
It is used in creation of tables which are used to present data in a more organized way.
It can be used in sharing of documents.
It can be used by researches to compare data using graphs and charts.
It has a word count feature which can be used in counting if words easily.
It can be used in creating web pages for organizations.
They are used by researchers and managers to create foot notes and cross references.
They are used in creation of letters, document, memos etc
Helps in saving on a storage device
Word processors are used in formatting and designing of simple office publications.
Features of a word processor;
Editing is the process of making changes to the existing content of a document
Common editing features include; Copying, Cutting, Pasting, Inserting, Deleting, Undo, Redo,
Selecting, Find etc
Undo is the feature that allows actions that have been performed to be reversed such that if some
text was accidentally deleted, then the action can be undone.
Redo It is the feature that allows actions that have been undone to be reversed.
Insert is an editing feature that allows adding text or graphics to a document
Delete is a feature that allows the user to erase text or graphics from a document.
Cut is a feature used for removing the original text from its original position onto the clip board
Copy is a feature that allows the user duplicate a section of the text and stores it on the clip board
Paste is an editing feature that allows the user to insert a whole text or a section of text
somewhere else.
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Find is a feature that allows the user to locate all occurrences of a particular character, word or
phrase.
Replace is a feature that allows a user to substitute existing characters, words or phrases with
new ones
Formatting is the process of making changes to the appearance of a document.
Levels of formatting
Character formatting which involves changing the font, font size, or font style of the text. It
involves applying the boldface, italics and underline text.
Paragraphs formatting; Involves changing the alignment of text, line spacing, indenting text,
tab settings and boarders
Section formatting allows the user to specify page numbers, headers and footers for different
sections or chapters of a document.
Document formatting allows the user to specify the overall page layout for printing. It involves
choosing the paper size (letter, legal, A4, A3), page orientation (portrait or landscape), changing
page margins (top, down, left or right) and the distances between the main body of text and the
edges of the paper.
Saving is the process of transferring data / information from memory to a storage medium such
as a floppy disk or a hard disk.
Print is the feature that allows the user to send a file to a printer to generate output on medium
such as paper.
Word wrap is a Microsoft Word feature which allows a user to type continually without
pressing the enter key at the end of each line.
Spelling checker allows a user to check the spelling of a whole document at one time or check
and correct the spelling or individual words as they are typed (Autocorrect).
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Thesaurus is a Microsoft word feature that suggest alternative words with the same meaning
(synonyms) for use in the document
Mail Merge is a feature that allows the user to create similar letters, mailing labels, and
envelopes to be sent to several people.
A table is an Ms Word feature which allows a user to organize information into rows and
columns.
Macros allows a user to record or save frequently used keystrokes and instructions which can be
executed later by running the corresponding macros
Clip art gallery allows a user to insert drawings, diagrams and photographs into a document.
Drop cap is feature used to enlarged the beginning letter of a sentence or paragraph
Footnote is a feature used to comment or add additional text found at the bottom of a page that
helps to refer to a document
Endnote is a feature used to comment or add additional text found at the end of the document
that helps to explain word in a document.
N.B. Footnotes are used for detailed comments while endnotes are used for citation of sources.
Header is the area in the top margin of each page where text can be entered.
Footer is the area in the bottom margin of each page where text can be entered.
Line spacing refers to the vertical distance between lines of text. It is a feature allows a user to
select a vertical or horizontal spacing between the characters depending on his need.
Changing Case is a feature that allows a user to type text in different cases. These cases are:
Lowercase: All characters appear in small letters.
Uppercase: All characters appear in capital letters.
Title case: All the first letters of each word in a sentence appear in capital letters.
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Toggle case: All characters changes from upper case to lowercases and vice versa.
Proof reading: is the process of reviewing a document to ensure the accuracy of its content. Proof reading tools include spelling and grammar checker and thesaurus, research, translate, word count etc
WYSIWYG (What You See Is What You Get) allow the user to print a document exactly as it
appears on the computer screen.
Advantages of word processing software over the ordinary typewriter
Easy and fast to make changes to the document
Have many features to create documents that look professional and visual appealing.
Documents can be previewed before being printed.
Documents can be saved for future reference and editing.
It is convenient in making letters and mailing labels.
It is possible to move blocks of text to different positions in the same document.
One can insert and delete lines of text.
The layout of the document can be altered before printing.
All typing mistakes can be corrected.
The document can be printed many times.
Text can be added to a document without having to type it again.
It can be used to mail documents unlike the ordinary typewriter.
It can create graphics such as shapes, frames etc.
It can be used to create WebPages.
One can easily count the words in the document using the word count feature.
It allows automatic insertion of footnotes and endnotes.
Disadvantages of word processing software
Data can sometimes be lost due to data corruption.
Some symbols aren’t easily accessible, which makes typing in different languages
that use a different alphabet is difficult.
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Requires a computer to edit or view documents which may sometimes not be there.
Require skills to use
Require electric power to function
Factors to consider when choosing a correct word processor:
1. The operating system you are using and check whether it can support which word
processors
2. If its user friendly
3. Consider the user’s need
4. Consider the cost of purchase
5. Whether it has most common features available with most word processors
6. Whether it comes with a warranty
7. Whether it has inbuilt automatic updates
8. Whether it comes with a documentation that has help and support.
TOPIC 5: ELECTRONIC SPREADSHEETS
A spreadsheet is an electronic worksheet that is used to organize data in rows and columns and
perform calculations on the data. It is an electronic worksheet that is used to organize,
manipulate and graph data.
There are two types of spreadsheets;
1. The manual spreadsheets
2. The electronic spreadsheets
A manual spreadsheet is the type of the spreadsheet commonly used type of book keepers as a
ledger book with many sheets of papers divided into rows and columns on which data is entered
manually using a pencil or a pen
An electronic spreadsheet is the type of the spreadsheet that uses the computer program that
enable the computer use to enter values in rows and columns to manipulate them mathematically
by the use of a formula.
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Uses of spreadsheets
It can be used by business men to record sales
It can be used by business men to produce invoices
It can be used to compile statements (e.g. Bank statements)
They are used for project planning and forecasting.
They can be use for creating personal lists such as shopping lists etc.
They are used for statistical analysis for instance in calculating average, mode, median
etc
They are use for budget planning such as weekly, motherly, annual budgets.
They are use for processing examinations results.
They are use in schools for creating class registers and mark sheet.
They are use in accounting by generating cashbook, ledger books, balance book etc.
Advantages of using spreadsheets
Handle a variety of applications
Easy organizing and processing of information
Automatic calculations
Enables easy formatting & editing of work
Speedy, flexible and efficient
Can be stored and retrieved at a later time
Reduces inventory (storage)costs
Easy sharing over the network
Neat work with various illustration like charts
Disadvantages of using Spreadsheets
It require a lot of resources like computers which are expensive
It is costly in terms of training personnel and resources needed
It is limited to power availability that is it can‘t work without power.
The whole work is lost in case of Virus attacks
Data can easily be change with ease by hackers.
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Advantages of using electronic spreadsheets over manual worksheets
It is easy to make changes and corrections to data on the worksheet.
The rest of the worksheet is recalculated whenever data on a worksheet changes.
It is fast with the help of built-in functions and macros.
Calculation is always accurate, provided that data and formulae entered are correct.
It is easy to create different kinds of charts or to change chart types.
Information on charts is updated automatically whenever related data on the worksheet
changes
Spreadsheets are much larger than manual worksheets
They can perform mathematical, statistical and financial calculations quickly and
accurately.
Cells in electronic spreadsheets can use information from other cells
Electronic spreadsheets can be stored and retrieved for repeated use.
Examples of spreadsheet program
include;
Microsoft excel
Corel Quattro Pro
Lotus1-2-3
Super Calc
VisiCalc
Multiplan
Microsoft excel (ms excel)
This is an electronic spreadsheet that can be used for practically manipulating of data and
figures.
Parts of Ms Excel document
A cell is the intersection of a column and a row.
A cell address is a unique address which defines the location of a cell in a worksheet (e.g. A1,
A2, Q7, etc)
Range is a rectangular selection of a worksheet containing two or more cells
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Work sheet is the biggest range consisting of all the cells in one sheet.
Work book is a collection of various worksheets
Range address is a range reference which has a format of top-left cell address and bottom-right
cell address (e.g. D12:F19)
Labels are text that identify the data and help to organize the worksheet. All label entries are left
aligned by default.
Column letter is a column that runs vertically on a work sheet and each one is identify by a
letter in the column header.
Row number is a row that runs horizontally on a work sheet and each one is identify by a
number in the row header.
Values are numbers to be used for calculations.
Cell reference is the location of a cell on a worksheet.
Types of cell references
Relative cell reference is a cell reference in which the cell address (e.g. B1 + C1) will be self
adjusted when the formula is moved or copied to another cell (e.g. B2 + C2)
Absolute cell reference is a cell reference in which the cell address (e.g. $B$2) is always fixed.
Mixed cell reference is a cell reference that uses absolute column and a relative row reference.
Example $A2 and A$2
Formulae and operators
A formula is a set of instructions for performing a calculation and displaying the resulting value
in the cell. A formula always begin with an equal (=) or a plus (+).
Types of formulae
Numeric (Arithmetic)
Text
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Logical
Numeric (Arithmetic) formulae is a formula used to perform calculations on values and uses +,
-, *, ^ and % numeric operators for calculation.
Examples=25+5, =A15*B1/B5
A text formula is formulae used to manipulate text. The text is normally enclosed in (quotation
marks) and to combine strings of text, use & (ampersand).E.g =if (B1>80,”Good”)
Logical formulae is statements that evaluate a condition. They result into 1 if true and 0 if false.
They use =, <,>,>=, <= and <>, AND, OR, and NOT to calculate various conditions. Example
Entry Results=5>4 - Results in true or1=5<A1 - Result in 1 or true if A1 has a value less than5=AND(A1=1,A2=2) - Result in 1 or true (if A1 contains 1andA2contains2
=OR(A1=1,A2=2) - Result in 1 or true (if A1 contains 1orA2 contains2)
=NOT(A1=0) - Result in 1 or true (if A1 contains any value but not
zero)
Basic mathematical operators used in spreadsheets
Symbol Description Example() Parentheses =B2*(C4+D5)* Multiplication =B2*C4/ Division =B2/C4+ Addition =(B2+C4)- Subtraction =(B2-C4)% Percentage =C5*60%^ Exponential =C4^2
Rules governing formulas
1. Always begin the formula with an equal sign or plus sign.
2. Type names of the functions correctly
3. Use the number of brackets on either side
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4. Do not leave unnecessary spaces between functions and brackets
5. Separate multiple arguments with commas
6. Enter the correct number of arguments in their correct order
Functions;
A function is a predefined formula that helps to perform common mathematical functions. Each
function has a specific order, called a syntax which must be strictly followed for the function to
work correctly.
Syntax order
All functions begin with the =sign. After the = sign, define the function name (e.g. SUM). One
or more arguments, numbers, and text or cell references enclosed in parentheses: if these are
more than one argument, separate each by a comma.
Types of functions used in spreadsheet
Statistical functions
Logical functions
Mathematical functions
Lookup functions
Examples of statistical functions
Function Example Description
Sqrt =SQRT(A4) Calculates the square root of a number
Count =COUNT(B1:B2) Counts the number of cells that contain value within a
range
Max =MAX(C2:C3) It returns the largest values in a set of values
Min =MIN(G1:G3) It returns the smallest values in a set of values
Mode =MODE(B2:C4) It returns the most frequently occurring value in a set of
values
Median =MEDIAN(B3:G8) it returns the middle value in a given range
Rank =RANK(A2,A2:A6,0) It returns the rank of a number in a list by comparing its
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size relative to the others
Average =AVERAGE(C2:C5) It returns mathematical mean of a set of values that contain
numbers
Logical function
If =IF(LOGICAL_TEST_,VALUE_IF_TRUE,V
ALUE_IF_FALSE)
It returns a specified value if a
condition is evaluated is found to be
True and another value to be False
Mathematical functions
Sum =SUM( A1:A2) Returns all the values in range of cells
Products =PRODUCTS(A3:B3) It adds values in a range of cells and
returns the result in the specified cell
Sumif =SUMIF(A1:A10) It adds values in the cells specified by
a given criteria or condition
Countif =COUNTIF(A1:A10) It counts the number of cell within a
specified range that meet the given
criteria
Lookup functions
Hlookup =HLOOKUP( It looks up data that has been
formatted by columns instead of rows
Vlookup It look up data that has been formatted
by rows instead of columns
N.B. In IF function, there are three items between the round brackets to be notice
IF (logical test, value_if_true, value_if_false)
1. Logical test; This is the first argument that you want to test for.
2. Value_if _true; This is what you want to do if the answer to the argument is Yes.
3. Value_if_false; This is what you want to do if the answer to the argument is No.
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Errors in excel and their possible causes and solutions
#DIV/0! Formula Error
Excel displays #DIV/0 error when a formula tries to divide a number by Zero or an empty cell.
For example = (A1/A2), where A1 contains 4 and A2 contains a null value (0). As shown below.
How to fix #DIV/0 error?
Simple, do not divide the value by Zero.
Change the Value of Cell A2 to a value that is not equal to 0.
Prevent the error from being displayed by using a Logical function IF
#N/A Formula Error
The N/A error is shown when some data is missing, or inappropriate arguments are passed to the
lookup functions (vlookup, hlookup etc.) of if the list is not sorted and you are trying to lookup
using sort option. You can also generate a #N/A error by writing =NA () in a cell.
How to fix #N/A error?
Make sure you wrap the lookup functions with some error handling mechanism. For example if
you are not sure the value you are looking is available, you can write something like =if (is error
(vlookup(…)),”not found”, vlookup(…)). This will print “not found” whenever the vlookup
returns any error (including #N/A)
#NAME? Formula Error
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This occurs when Excel does not recognize the text in a formula. The most common reason why
you see this error is because you misspelled a formula or named range. There are few other
reasons why this can happen. For example =SU(A1:A3) as shown below.
How to fix #NAME? Error?
Simply correct SU to SUM
Make sure you have defined all the named ranges you are using in the formula.
#NULL! Formula Error
This error occur when you use incorrect range operators. For example the formula =SUM
(D30:D32 C31:C33) returns a #NULL! error because there is no separator between range 1 and
range2.
How to fix the #NULL! Error?
Make sure you have mentioned the ranges properly.
#REF! Formula Error
Excel displays #REF! Error when a formula refers to a cell that is not valid.
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How to fix the #REF! Error?
First press CTRL+Z and undo the actions you have performed. And then rethink if there is a
better way to write the formula or perform the action (deleting cells).
#NUM! Formula Error
This is number error that you see when your formula returns a value bigger than what excel can
represent. You will also get this error if you are using iterative functions like IRR and the
function cannot find any result. For example the formula =4389^7E+37 returns a #NUM! Error
How to fix #NUM! error?
Simple, make your numbers smaller or provide right starting values to your iterative formulas.
###### Error
You see a cell full of # symbols when the contents cannot fit in the cell. For example a long
number like 15000000 entered in a small cell will show ####s. Also, you see the ###### when
you format negative numbers as dates.
How to fix the ###### error?
Simple, adjust the column width. And if the error is due to negative dates, make them positive.
#VALUE! Formula Error
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Value error is shown when you use text parameters to a function that accepts numbers. For
example the formula = (A1+A2+A3) returns #VALUE! Error
How to fix the #VALUE! Error?
Make sure your formula parameters have correct data types. If you are using functions that work
on numbers (like sum, sum product etc.) then the parameters should be numbers.
TOPIC 6: ELECTRONIC PRESENTATION
Presentation is a collection of data and information to be delivered to a specific audience.
Electronic presentation is software used to create presentations which can communicate ideas
and other information to a group or audience. The presentation can be viewed as a slide show on
a large monitor or a projection screen. It involves presenter and the participants with visual
information which complements the talk. Examples of presentation software;
Microsoft PowerPoint
Corel presentations
Lotus Freelance
graphics
Harvard Graphics
Micro media director etc
Functions of a presentation
It allows text to inserted and formatted.
It is used to insert and manipulate graphics, images or animations with objects
It has a slide show system to display the designed slide content.
Qualities of a good power point presentation
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Principles of a good presentation
Avoid excessive visuals and slides to detract you from your message.
Be the primary source of presentation but not power point slides.
Use flowcharts and photographs to illustrate more abstract points.
Think carefully about the sequence or the flow of your slides.
Factors to consider when designing a good presentation
Identify the goal of the presentation
Use slide design effectively
Include the title page with your name, contact, date and session topic for the presentation.
Include only the main points
Present information consistently
Include only one main concept per slide.
Include graphics, charts, and videos to keep your audience alert
Avoid fancy fonts
Don not includes too many slides in your presentation.
Avoid excessive use of animations and transitions
Common terms used in Microsoft Power Point;
Slide is an individual page in a presentation. They are normally viewed using projectors.
Title slide is the first slide in your presentation normally with a heading and sub-heading.
Slide Master/ Master Slide is a single slide that controls all other slides in a given presentation.
Any changes made to it affect the rest of the slides respectively.
Handout is a combination of 2 to 6 slide images on a single page.
Speaker’s notes are notes that help in the actual delivery of a presentation. Power point lets you
enter and print a notes page for each slide
Colour scheme is the overall colour design for all the slides in a presentation
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Timing is the period of time a slide stays on the screen during a slide show.
Templates are already created files stored in the computer for reference purposes that defines
what your presentation will look like. Power point provides over 100 professionally designed
templates containing proven layouts, color schemes and background textures.
Slide Layout is the given design of a slide showing divisions/areas or sections of a slide where
work can be done. E.g. title only and blank slide layouts
Animations are visual effects applied to individual items in a slide such as graphics, images, titles
etc.
Transition is a way a slide moves off the screen and the next slide appears.
Wizard is a series of automatic steps that guides you through a task. It helps the user to choose a
style and design for the slides.
Transitional looping is a facility which sets up the presentation to run continuously until it is
stopped by the presenter.
Action buttons are built in button shapes that you add to a presentation to use as hyperlink.
Viewing a presentation
Power point provides five different presentation views i.e.
Outline view
Slide sorter view
Slide view
Notes page view
Slide show view
Slide view shows the user how the slide will appear when printed or displayed. It is similar to
page layout in a word processor for windows. All text, graphics and other media elements appear
in slide view.
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Outline view enables one to outline content much as you would in a word processor to enter,
arrange and edit textual information. It is useful in organizing one‘s thoughts and developing
textual content for a presentation.
Slide sorter view provides a light table for viewing multiple slides. When selected, this view
arranges small thumbnail presentations of your slides, complete with text and graphics, rows and
columns.
Notes page view allows you to insert edit and delete reminder notes for yourself on each slide. It
allows you to use a slide‘s notes page for creating extended notes as an audience handout. It lets
you enter text and graphics in a notes place holder located below the image of the slide.
Slide show view (Also called on-screen presentation) is a view that takes up the full computer
screen, like an actual presentation. It lets you see how your graphics, timings, movies, animated
effects, and transition effects will look during the actual presentation to the audience.
Advantages of presentation software over traditional chalk and talk
1. It provides a wide variety of presentation formats and layouts for the slides.
2. Allows addition of multimedia components such as clipart images, video clips and audio
clips.
3. Allows setting of timing for the slides so that the presentation automatically displays the
next slide after a predetermined period of time.
4. Allows application of special transition effects on each slide.
5. The presentation can be viewed and printed in different formats.
6. Provides no dusty environment
7. Provides security through the use of password
8. Provides different print formats e.g. Handouts, slides.
TOPIC 7: DATABASE
A database is a collection of related information stored for a particular purpose. It is a collection
of interrelated data about a particular subject or for a specific purpose which allows a user to
retrieve, update and manipulate data any time. Examples of database include;
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Telephone books (directories)
Customer address books
Dictionaries
Television guides etc
School registers
National voters register
National passport register etc
Characteristics of databases
The data is arranged in columns (fields) and rows (columns).
Each column has similar data items.
Each row contains information belonging to a single individual.
Qualities of a good database
Should make the best use of the computer resources
Should be fast
Should interface smoothly with the existing facilities
Should be updatable
Should provide easy access to authorized users
Should preserve data integrity
Should ensure the privacy of data
Database Management System (DBMS) is a collection of programs which allows a user to
create access and maintain a database.
Examples of DBMS
Dbase I, II, III, IV,V
Microsoft access
Oracle
Lotus Approach
SQL (Structured Query Language)
Functions of database management systems
It enable the user to add and delete records
It enable the user to update and modify the existing records
Provides an interface to the user to enter data
Ensure security for data against unauthorized access
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It enable users to filter out records by meeting certain given criteria
Enables the creation of summary reports
Types of database management systems/ models
Database model refers to the way data can be stored, organized and manipulated.
There are five commonly logical types of database models;
1. Flat file model
2. Hierarchical database model
3. Relational database model
4. Network model
5. Object oriented model
Flat file model is a database made up of only one table. It is easy to set up and use
Hierarchical database is a type of database model in which data is organized into a tree-like
structure. Each record contains one root segment and a variable number of subordinate segments
that define a field within a record.
A relational database is a database which can take information from two or more database
tables and combine them into a new table or report.
NB: A relationship determines the way in which the details in one table are related to the details
in another table. It can be a one to one relationship, one to many or many to many relationships.
The network databases (Online databases) is a type of database model in which data
relationship, items and the database itself is link to each other in form of a network. Combines
records with link which are called pointers; the pointers physically establish the relationships
between records.
Object oriented model is a database model that appears as independent objects which can relate
with each other.
Advantages of using a Database Management System over manual based systems
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Databases allow control of data redundancy because most of the data is storing in one
place hence less duplication
It provides security and authorization to its users.
Database management system provides possibilities for data backup and recovery.
It provides possibilities of data access via network connection.
Data is entered, stored, modified and accessed by methods that are not affected by
application programs.
Database management system eliminates data duplication that minimizes costs of
maintenance.
Disadvantage of using a Database Management System over manual based systems
There is lack of confidentiality, privacy, and security when information is made available
to user from the remote location
Data quality is compromised when there is increasing number of users accessing data
directly.
It provides threats to data integrity when different people are tempting to update the same
data at the same time.
They are also difficult and time consuming to develop.
Database management systems are expensive to set up and to maintain because of their
complexity and efficiency.
It creates user resistance to change from traditional file orient system to database
management system
Common terms/words used in Microsoft Access
An object is a compilation of table, quarry, form, reports, pages, modules and macro in a
database
A record is a row in a table that contains information about a given person, product or event
A table is a primary element used to collect data that are related to a particular subject organized
into rows (records) and columns (fields) similar to an electronic worksheet.
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The table structure is the number of fields, field names, and field lengths and data types in the
database table
Table relationships are the associations of data between tables e.g. one-to- one & one-to-many
A file is a combination of related records.
A field is a column in a table that contains a specific piece of information within a record
A field name/Label is a title or a name of a particular column.
Field Length is the maximum number of characters that can be stored for data in a particular
field
Field properties refer to specific characteristics of a particular field.
Validation is the process of checking of input data for errors (e.g. data type) before processing
Data verification is the checking for mistakes when data is copied from one place to another
Data type (field type) is the type of value that you enter into the field. This is a column that
specifies data that will be stored in the field.
Examples of data type (Field type)
Data type (Field type) Description
Text (Short Text) Allows characters (numbers) up to 255 characters that can be calculated
Memo (Long Text) It is used for lengthy descriptive text and number which allow storage of
data up to 64,000 characters
Number Allow storage of numbers only for calculation
Date/time Allows date or time or a combination of both e.g. Date of birth
Currency Is a numeric field automatically assigned a currency sign
Auto number Creates a unique sequential number for each record
Yes/No Allows storage of logical or Boolean values of Yes/No, On/Off,
True/False
Object Linking and
Embedding (OLE object)
Allows a linkage to pictures, photographs & other objects created in
another program such as word document, excel spreadsheet
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Lookup wizard Allows you to link the field to another table
Hyperlink Allows a link to an internet, internet site or to another location in the
database
Examples of Field properties
Field properties Description
Field size The maximum number of characters needed for any data item (by default 50)
Format The appearance of that particular item in that particular field
Indexed It specifies whether or not duplicates in the field should be allowed in order
to speed up the data search, sort, filter, etc.
Capitation This is a default label in a form or report e.g. DOB for date of birth, L/name
for last name, F/name for first name, M/S for marital status, etc.
Input mask Specifies the pattern or predefined format for data to be entered in that field
e.g. (--/--/--) i.e.dd/mm/yy for date or (-- :--:--) Hh: Min: Sec as for time, etc.
Others are :!( 999} OOO-OOOO for telephone number.
Default value A value that appears in the field automatically even before you enter there
anything i.e. it works as a placeholder e.g. MSMN/ _, U0063/ _, for index
no., 0.0 for numeric fields, etc.
Field validation rule An expression that defines data entry rules i.e. it limits values that can be
entered in that field e.g. "F" or "M" for sex, >=10 for age, "married" or
"Single" for marital status, etc.
Validation text An error message that appears when a validation rule is violated e.g. "Please
only For M for sex."
Required (Yes/No) Specifies whether or not an entry must be entered in that field i.e. if yes you
must type an entry but if No, you may proceed without entering anything.
Decimal places Specifies whether or not number and currency values should have decimals.
If yes, how many.
Allow Zero length A provision for a field to be left blank in case of unavailable data to be
entered later even if the setting for required is yes. To enter a null, leave the
required property as No and leave the field blank e.g. a company without a
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fax machine/no., etc.
Database objects
A database is made up of several objects, grouped into a single file; among them include;
Database objects Description
Tables Are primary structures in a database that holds raw data
Queries These are tools used to select records from one or more tables in a database.
They do questioning tasks like how many boys from stream A
Forms These are graphical interfaces that are used to display and edit data. Forms
can be developed from a table or a query.
Reports These are tools that enable one to preview and print data in a meaningful
format.
Pages Are tools used for creating/editing world wide web pages
Macros These are simplified programming languages which you can use to add
functionality to a database
Modules These are collection of declaration, statements, and procedures that are stored
together as a unit, modules, like macros, are objects one can use to add
functionality to a database.
Query criteria
A query criterion refers to as expression in Microsoft office access. Criteria are similar to a
formula.
Consider the following criteria use in query;
Criterion Query result
“Kampala” Returns records where the location field is set to Kampala.
Not “Jinja” Returns records where the location field is set to a location other than
Jinja.
Like U” Returns records for all countries whose names start with "U", such as
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UK, USA, and so on.
Not Like U” Returns records for all countries whose names start with a character
other than "U".
Like “*Lira*” Returns records for all locations that contain the string "Lira".
Not Like “*Lira*” Returns records for all locations that do not contain the string "Lira".
Like “*ina*” Returns records for all locations whose names end in "ina", such as
China and Argentina.
Not Like “*ina*” Returns records for all locations that do not end in "ina", such as China
and Argentina.
Is Null Returns records where there is no value in the field.
Is Not Null Returns records where the value is not missing in the field.
““(a pair of quotes) Returns records where the field is set to a blank (but not null) value. For
example, records of sales made to another department might contain a
blank value in the location field.
Not”” Returns records where the location field has a nonblank value.
““Or Is Null Returns record where there is either no value in the field, or the field is
set to a blank value.
Is Not Null And Not”” Returns records where the location field has a nonblank, non-null value.
>=“Jinja” Returns records of all locations beginning with Jinja and continuing
through the end of the alphabet.
Like“[A-D]*” Returns records for location whose names start with the letters "A"
through "D".
“Uganda” Or “USA” Returns records for Uganda and USA.
In (“Kampala”, “Jinja”) Returns records for all locations specified in the list.
Right ([Location],1)= “X” Returns records for all countries/regions where the last letter is "X".
Len ([Location])>10 Returns records for locations whose name is more than 10 characters
long.
Like "Chi??" Returns records for locations such as China and Chile, whose names are
five characters long and the first three characters are "Chi".
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Different keys used in database
Primary Key is a key that uniquely identifies each record in the table. The primary key cannot
be the same for two records.
Foreign Key is a copy of the primary key in another table
Composite Key is a primary key that is comprised of two or more fields. It can also be called a
compound or concatenated key.
Wildcards
A wild card is a symbol used to replace or represent one or more characters. Wildcards are
typically either an asterisk (*), which represents one or more characters or question mark (?),
which represents a single character. A wildcard refers to a character that can be substituted for
zero or more characters in a string.
Wild card Description
? Allow a single character or digit at the position marked by?
* Allow any characters, digits, quantity at position marked by*
# Allow access to match any single numerical digit
Example:
J?lly will find Jolly, Jelly,Jilly only
Am* will find only words that begins with “Am” only such as America, amicable
FACTORS TO CONSIDER WHEN DESIGNING A DATABASE
The number of tables needed.
The number of fields and the field names
Unique identifiers of fields with uniquevales
Relationships between the tables if any
Practicability of the database
TOPIC 8: WEB SITE DESIGNING
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Web Design and Publishing is the process of planning, creating, manipulating, saving and
uploading hyperlinked html documents (web pages) to a computer network so that they can be
viewed via web browsers.
A website (or Web site) is a collection of related hyperlinked web pages hosted on a particular
web Server on the World Wide Web.
Each Web site may contain one or more web pages. Each site has a home page which is the first
document/page users see when they enter a site. The site might also contain additional documents
and files which must be hyperlinked. Each site is owned and managed by an individual, company
or organization.
A Web page is a document, typically written in HTML that is accessible via HTTP, a protocol
that transfers information from the Web server to display in the user's Web browser. It is written
in HTML (Hypertext Markup Language). A Webpage contains hyperlinks to other pages or sites.
A hyperlink is a reference or navigation element in a document to another section of the same
document or to another document that may be on a different website.
HTML uses blocks of text enclosed within angled brackets which are referred to as HTML tags.
These tags are codes which describe the structure and formatting of the document (how the web
page is displayed by the browser). For example, there are tags to describe normal text paragraphs,
headings, bullet lists, etc.
Web publishing process
This involves;
Web designing
Web authoring
Web authoring software
Web site hosting
Web site content management.
Web designing
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Web designing is a process of conceptualizing, planning, and building a collection of electronic
files that determine the layout, colors, text styles, structure, graphics, images, and use of
interactive features that deliver pages to your site visitors.
This is the initial process of web publishing through which a web page is created. It’s about
organizing web content so that it can be easily found and easily read and is attractive to visitors.
Web authoring
Web authoring refers to designing and creation of a Web site, ranging from writing the site's
underlying code to writing the text to managing the site's upkeep. This can be done directly by
writing the html code, or using html tools that operate in the background to create the code while
the author is using a WYSIWYG interface.
Web authoring software
This is a category of software that is used to design web pages, it may not require one to have
any knowledge of HTML coding because it offers Web page design wizards and different web
page design templates for the user to pick from and simply insert content. The software will
generate the required HTML coding for the layout of the Web pages in the background based on
what the user designs. Examples of commonly used authoring software include Dreamweaver,
and Microsoft FrontPage, Note pad
Web site hosting
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Website hosting is a service that allows individuals and organizations to have their own websites
accommodated on a particular web server from which they are accessed by others on the World
Wide Web. Web hosts are companies that provide space (web hosting) on a server they own for
use by their clients. Some web hosts provide free services while others charge a fee. Free web
hosting is advertisement-supported web hosting, and is often limited when compared to pay
hosting.
A website can also be hosted on a server in a home or on a local area network.
A web page is created using a language called, Hypertext Markup Language, better known as
HTML Code. You can write your own coding within a plain text editor, such as Notepad, or use
an HTML editor, which will write the code for you.
HTML codes, also referred to as HTML tags, are enclosed by the lesser than (<) and greater than
(>) brackets and may be written in capital or lower case letters.
The opening bracket is followed by an element, which is a browser command, and ends with the
closing bracket.
An element may also be followed by attributes, which are words describing the properties of the
element, and further instruct the browser.
Attributes are only contained in the opening HTML tags to the right of the element and are
separated by a space and followed by an equal (=) sign.
The value follows the equal sign and is enclosed in quotes.
Web site content management system
A content management system (CMS) is a system that provides a WYSIWYG interface to
manage the content of a website. This involves adding new content, editing, or modifying
existing content and removal of unwanted or expired content. It allows the content manager or
author, who may not know Hypertext Markup Language (HTML), to manage the creation,
modification or removal of content from a website without needing the expertise of a webmaster.
Examples of CMS include;
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Example of basic document structure
<HTML>
<HEAD>
<TITLE>your document title goes here</TITLE>
</HEAD>
<BODY>
Your document text goes here
</BODY>
</HTML>
HTML
The very first tag in your document: <HTML> and the very last: </HTML>
HEAD
The second tag in your document. Enclosed within the beginning tag: <HEAD> and the ending
tag: </HEAD> is information about the document that will not display in the body of the
document.
TITLE
The document title, which is enclosed with a begin title tag: <TITLE> and an end title tag:
</TITLE>, all of which is enclosed with the HEAD tags above. The title does not display as part
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of the document itself, but appears in the browser window title. It is also what is used to name
your document in a bookmark list.
BODY
The complete text of your document is wrapped by a begin body tag: <BODY> and an end body
tag: </BODY>.
Characteristics of a good web site
1. It should be easy to navigate with well arranged, easy to see navigation buttons.
2. Simple and clear layout of sections and content which makes it user friendly ie find content
easily.
3. It must be pleasing to the eye to encourage visitors to the site.
4. It should load quickly to avoid disappointing potential visitors to the site.
5. It should have readable font web safe eye pleasing colours so that visitors can read the
content easily.
6. It should be interactive with contact information, possibility of e-mail, online communication
forum and chats. Message boards etc.
7. Should have active links which enable visitors to access other references.
8. Should be frequently updated and must have a dated of last update.
9. The web pages must have web page titles and brief summaries about the page or site
Project work on web designing
You are required to design five web pages (use any web publishing software) for your school
taking into considerations the properties of a good web site.
Page one is the Home page which must include;
(i) A welcome note and information on the schools location and motto
(ii) The schools email address
(iii) The web links to the other pages
(iv)The navigation bars
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(v) Company logo
Page two should show bullet list of departments available in the school. Add a link to the
school website for further information.
Page three should contain other facilities offered in the school e.g. swimming, school bus,
and internet services.
Page four should have brief information on your dormitory/house and a simple definitions
list stating the chorus of your house.
A table indicating 5 names of your dorm mates showing their Bio data(age, sex, home
town/district
Insert a relevant form control
Page five should have photo gallery of at least five images
Terminologies used in web designing
These are brief definitions of some of the common terms used in web design and publishing
Bookmark: A bookmark is an anchor tag that defines and links to a specific location in an
HTML document. Bookmarks are useful when you have long pages that are divided into logical
sections, or when you want to jump from one central list of links to multiple locations on a page.
File Transfer Protocol (FTP): The protocol used for copying files to and from remote computer
systems on a network using TCP/IP, such as the Internet.
HTML:(Hypertext Markup Language) A tagging system used to code documents so that they
can be published on the World Wide Web and viewed with a browser
HTTP: (Hypertext Transfer Protocol): The client/server protocol used to access information on
the World Wide Web.
HTTPS: (Hypertext Transfer Protocol Secure) is a combination of HTTP with the SSL/TLS
protocol to provide encrypted communication and secure identification of a network web server.
HTTPS connections are often used for payment transactions on the World Wide Web and for
sensitive transactions in corporate information systems.
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HYPERLINK: The text or graphic that users click on to go to a file, a location in a file, an
Internet or intranet site, page, location, and so on. Hypertext is text with hyperlinks.
INDEX PAGE: The home page or URL of a website, usually serving as an introduction and
having links to other pages in the website
DOMAIN NAME: The unique name that identifies an Internet site. A domain name is an
identification label that defines a dominion of control on the Internet, based on the Domain
Name System (DNS).
IP ADDRESS: An (Internet Protocol address) is a numerical label that is assigned to any device
participating in a computer network that uses the Internet Protocol for communication between
its nodes.
JPEG / JPG:(Joint Photographic Experts Group) A graphics format used for photos and other
graphics with more than 256 colors.
Page title: The text that is displayed on the page banner of a Web page and in the title bar of a
Web browser.
URL: (Uniform resource locator) is the alphanumeric address that Web visitors use to locate
your Web site on the World Wide Web.
Tags: HTML tags are codes, of keyword elements enclosed by the lesser than (<) and greater
than (>) brackets, which give commands to a browser. e.g. <u> is an HTML tag that tells the
browser to underline text on the webpage.
Web authoring software: A Web site development program that allows Web pages to be
visually created like a desktop publishing program. It generates the required HTML code for the
pages and is able to switch back and forth (in varying degrees) between the page layout and the
HTML.
Web Browser: Is application software which enables a user to display and interact with text,
images, and other information on a Web page (Examples: Opera, Google Chrome, Mozilla
Firefox, Internet Explorer, Netscape, etc.)
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Web mail provider: A hosting company that primarily provides end users access to internet
services such as e-mail
Web server: A computer that stores and delivers (serves up) websites and their related files for
viewing on the Internet
Webmaster: A person who creates and manages the information and content, organizes and
maintains of a Web site
WYSIWYG: (What You See is What You Get) implies a user interface that allows the user to
view something very similar to the end result while the document is being created.
Homepage
It is the first page (starting page) of a website. It is the table of contents for a website.
A web page
A web page is an electronic document or files of information stored on the web /website. It can
contain text, animations, audio, and video that are connected to other documents.
What to consider when designing a web page
The target or primary audience of the web site.
The impression you wish the site to create to your visitors.
The purpose of the website. Whether personal, commercial or educational. This helps to
determine the design for it.
The browser types or version likely to be used by your primary audience to determine the
nature of materials to use in the website
How to organize the site links and web pages to enable easy navigation through the site by
visitors.
To obtain the relevant content to include in your page.
Obtaining permission to use other people’s copyrighted content or to link to other people’s
sites this protects you from any possible legal problems concerning copyright violation.
Qualities of a good web page
Should have a feedback
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Should have good navigation buttons
Should load quickly
Should have fewer graphics. Too much graphics can make it to take too long to load,
take up too much space and client computers may not support different colour depths.
Should have a web page title and a summary about the page
Should have dates of the latest updates
Should have links to other pages or to sections within that page
Components of a web page
a) Page titles;
These indicate the name of the website
b) Buttons and icons
These are tools used to navigate through the website
c) Horizontal line separators
These are parallel lines separating different sections of a web page
d) Graphics (Images)
These are pictures used during the designing of the website.
e) Frames
These are used to provide more flexibility to a website
f) Sound buttons
These are buttons used to provide access to sound clips, interviews, music extracts etc, in
case a search engine is to produce sound.
g) Animations
These are components providing movement and actions in a web page. They are used to
make a web page more lively.
h) Hyperlinks
These are colored and underlined text or graphics that one clicks and go to a file, a location
in a file or an HTML page on the internet.
A hyperlink is a word, group of words or image that you can click on to jump to a
new document or a new section within the current document.
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i) URL (Uniform Resource Locator)
This is an internet or web address describing the location of the server where the
website is located.
j) HTML lines
These are horizontal lines in an HTML page.
k) Comments
Comments can be inserted into the HTML code to make it more readable and
understandable. They are not displayed by the web browsers.
l) Ordered lists
These are lists with items marked with numbers.
1. Coffee
2. Milk
3. Black tea
m) Unordered lists
These are lists with items marked with bullets (typically small back
circles e.g.
Coffee
Milk
Black tea
n) Definition lists
It is a list of items with a description of each item.
o) Forms
These are used to select different kinds of user input. They are used to pass data to a server. They can contain elements like text fields, checkboxes, and radio buttons, submit buttons etc.
p) Text field
It is an input field that a user can enter text into;
e.g.
First name:
Last name:
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q) Password field
Is an input field that a user can enter a password
into e.g.
Password:
r) Radio buttons
These are buttons in a web page that lets a user to select only one of a limited number
of choices.
They look like;
s) Check box
This lets a user select one or more options of a limited number of
choices. e.g.
I have a bike
I have a car
t) Submit button
This is a button used to send data to a server. e.g.; Username:
u) Drop down arrows
These are used to open dropdown menus
. A website
A web site is a collection of related or hyperlinked web pages.
TOPIC 9: DESKTOP ENVIRONMENT
Desktop environment
A desktop is the first seen by the user when a window is open. It consist of features mainly
shortcuts icons programs such as my computer, recycle bin web browser etc.
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Shortcuts are icons on the desktop that provides a user with immediate access to a program or
file.
Icons are the smallest graphical or pictorial representation of several commands, an application,
a shortcut etc. it may represent a file, a folder, hardware utility, printer, disk drives etc.
Major icons on the desktop
1) My computer
2) Recycle bin
3) Network places (network)
4) My documents
My computer
This is a component or a system folder in the Microsoft windows file manager windows explorer
which allows the user to explore the content of their computer drives as well as managing their
computer files.
Recycle bin
Recycle bin is also known as Trash. It is a temporary storage for files that have been deleted in
the file manager by the user, but not yet permanently deleted for the file system.
My network places
My network place is an icon on the desktop that displays shortcuts to shared computers, printers,
and other resources on the network. My network place is open by clicking start button, and then
you click my computer then click my network location.
My documents
My document is a name of a special folder on the computer’s drive that the system commonly
uses to store a users documents, music, and pictures, downloads, and other files. It is a user’s
personal folder in which he/she can store documents, graphics, and other personal files.
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Parts of a desktop
Start button
This is a button located on the left bottom corner of a desktop. It is a button when clicked takes
you to the other programs.
Task bar
A task bar is a located at the bottom of the screen that contains the active tasks that are currently
running on the computer.
Start menu
A start menu contains icons for programs, folders and access to control functions plus other
menus
Notification area
Notification area is an area that contains icons of special programs including the time and date of
the day.
All programs
These are lists of applications installed on the computer which can be opened from the list.
Search programs and files
Changing the appearances of a desktop
Such as desktop background, screen saver, and windows colour.
Procedures of changing desktop appearances
Right click on the empty space on a desktop
From the drop down menu choose personalize option
Adding a program to appear on a desktop
Procedures:
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Click the start button
Select the desired program and right click
Click show on the desktop
Aligning icons on a desktop
Point the cursor on any empty space of a desktop
Choose the view option which will display a list of other options or rearranging icons on
the desktop
Select the desired option and click
File management
This is a system that an operating system or program uses to organize and keep track of files.
Any document is stored as a file by the computer. Each file has a file name. Each file name has
two parts: file name and file extension. By default the computer allocates a name to a file which
you can change.
A folder
A folder is a specific named location on a storage medium that contains related documents. It is a
virtual container within a graphical user interface in which groups of computer files and other
directories can be kept and organized..
Creating a folder
Right click the empty are on the desktop
Select new from the drop down menu that appears
Select folder
Give the appropriate name to the folder
Then press the enter key on the keyboard
Renaming a folder
Right click the folder
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Select the option rename
Give the appropriate new name to the folder
Then press the enter key on the keyboard
Moving a folder
Point the cursor to the folder you want to move
Hold down the primary mouse button
Move the folder the desired location or another folder on the screen
Then release the mouse button.
Deleting a folder
Right click on the folder
Choose the delete option
Then click yes
A file
A file is a collection of related data.
Types of files
Regular files are files used to store data in the form of text or binary
Directory files are files that contain information used to access other files.
Special files are files that defines physical devices for the system
Video files for video development.
Web files for web activities such as wed development
System files are files that enable computer to function with the operating system
Image files used to develop photos and graphics.
Audio files for digital audio such as music sound etc.
Backup files for copies of files in a computer which can later be accessed in emergence
cases.
Archived file is a computer file used to store electronic information or documents that you no longer need to use regularly
Creating a file
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Click on the file menu or the office button in the program you are using
Select the first option new and the click on it.
A dialogue box will appear and then click create
After working with the new file, click the file menu
Select save as option to give the file appropriate name
Then save the file either in my computer or my document or on the desktop by clicking
saves.
Saving a file
Click on the file menu or the office button
Select save as option
Give the file the appropriate name
Choose where to save the file either in my computer or my document, or on the desktop
And then click save
File name and file extension
A computer file is made up of two parts that a file name and a file extension which is separated
by a dot.
A file name is a name used to uniquely identify a computer file stored in a file system. It is
associated with the content.
On the other hand a file extension is a part or suffix at the end of a file name which identifies
the type of file it represents.
It is the end part of a file name that is separated by a dot, containing characters based on the
program used to create the file example tobbyecat. doc, meaning that tobbyecat is the file name
and .doc is the file extension.
Functions of a file extension
1. To identify the file type.
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2. It identifies what program to associate the file with and how to properly open it using the
correct program.
3. It helps to easily locate files.
Common file extension
NO FILE EXTENSION FILE TYPE EXAMPLE
1 .doc Microsoft word Tobbyecat.doc
2 .xls Spreadsheet Mybook.xls
3 .ppt Presentation DMO.ppt
4 .db Database ICTdeprt.db
5 .pub Publication Cards.pub
6 .rtf Rich text format Invitation .rtf
7 .txt Unformatted text document Tobby.txt
8 .pdf Portable document format A level ICT.pdf
9 .exe Executable file Ecat.exe
10 .bat Batch file Autofile.bat
11 .gif Graphical interchange format. A digital image
file format
Photo.gif
12 .jpeg or mpg Joint photographic experts group. A digital image
file format
Nighty.jpg
13 .png Portable network graphics Tobby.png
14 .mpeg Moving picture expert group
15 .AVI Microsoft windows movie file
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16 .BPM Graphical Bit Mapped File used in windows paint
17 .HTML Hypertext Markup Language is a Web page files
containing HTML or other information found on
the Internet
18 .SYS Various types of System files – usually drivers to
control devices
19 .xml Extendable markup language
File hierarchy
A file hierarchy defines directories (also called folders), which can contain files and other
directories.
The top-most directory in any file system is called the root directory.
A directory that is below another directory is called a subdirectory.
A directory above a subdirectory is called the parent directory.
File path
A file path or a file directory specifies a unique location of a particular file in a file system.
Example; C:\My Documents\assignments\English\nouns.doc
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ROOT DIRECTORY
DIRECTORYDIRECTORY
SUB DIRECTORY SUB DIRECTORY
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Root directory: C:\
Directory(folder): \My Documents\
Subdirectory(subfolder): \English\
file: \nouns.doc
A file path can be observed in the address bar of a particular window in which the file is being
used. A file path or directory consist of location of a file, user profile, folder, sub folder file, file
name and file type.
Example; D:\visitor\my document\sub ICT\S5 results.doc
D:\ file location
Visitor\ user profile
My document\ folder
Sub ICT\ sub folder
S5 results\ file name
.doc file type
Viewing file extension
Click start button
Click control panel
Click the tools drop down menu
Click folder options
Click view
Uncheck Hide extension for known file types
Click apply, then ok
Managing computer files
When using files on your computer system, there are some aspects one needs to put under
consideration such as storage of files, security for the files, backups, disk space usage and
defragmentation.
Such considerations include;
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1. Create backups of your files that keeping copies of your files away from computer
to avoid some events such as data loss, disasters like fire out break etc.
2. Install antivirus software to protect your computer against malware.
3. Use file compression schemes to save disk space for files which takes up large
storage space.
4. Use disk fragmentation tool to allow faster computer processing.
5. Protect your files using encryption or password
How to create a file with password
Click on the file menu or the office button in the program you are using
Click on save as option
Click on the tool menu at the bottom of the dialogue box
Click on general options
Type the password of your choice and click ok
Retype the same password
Then click ok
File backup
File backup refers to the activity that involves creating copies of files away from the computer,
which can later be accessed or retrieved.
There are two forms of file backups
1. Local backup (offline backup)
It involves backing up important files to external storage devices such as flash disks, memory
cards, external hard disks, compact disks, Digital versatile disks, magnetic disks, zip drives etc.
2. Internet backup( online backup)
This involves sending your files to another site on the internet computer for safe keeping. You
can even create a backup on your email account.
Importance of backup
To recover from data loss in case of accidental deletion, data theft, data corruption
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To safely stored data away from the computer
To ensure disaster data recovery plan
TOPIC 10: SYSTEM START-UP AND CONFIGURATION
System Startup is a general term used to describe the process of preparing the computer,
operating system, hardware, or software for operation. This action is more commonly referred to
as the boot or boot up.
The first thing a computer has to do when it is turned on is start up a special program
called an operating system.
As the computer is switched on, it does the Power – On Self Test (POST) before it starts.
The POST consists of RAM check, CMOS check, HDD controller check (Disk Drive
controller check).
In case one of the checks fails, then an appropriate error message is displayed on the
screen or an abnormal number of beeps are sounded. The whole process is called
BOOTING.
Computer booting
Booting is the process of starting or restarting a computer which involves loading an operating
system into memory.
Types of computer booting
There are two types of booting;
1. Cold booting
2. Warm booting
Cold booting
It is the process of starting a computer which has been totally off which involves loading the
operating system into memory.
Steps involved in cold booting
Switch on the main power source (i.e. socket)
Switch on the uninterruptible power supply
Switch on the system unit
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Finally switch on the monitor
Power on self test is conducted by the BIOS, Bootstrap loads the OS into RAM then the
desktop is activated
Warm booting
It is the process of restarting (resetting) a computer that is already turned on. In the windows
environment, it is normally performed by pressing Ctrl+Alt+Del keys on the keyboard.
Reason for warm booting
I. Whenever the computer devices such as keyboards, mouse, etc. stop responding to
commands issued to them.
II. After installing a software or hardware onto your computer.
III. After scanning for viruses.
IV. After uninstalling a software
V. In case one wants to recover from errors
VI. When a computer freezes
Computer booting processes
i. The power supply sends an electrical signal to the motherboard and other devices located
in the system unit.
ii. The CPU resets itself and looks for the ROM that contains the BIOS.
iii. The BIOS executes the Power on Self Test (POST) to ensure that all the computer
hardware is connected properly and operating properly.
iv. The results of the POST are compared with the data in the CMOS chip on the
motherboard.
v. If the POST is completed successfully, the BIOS look for the boot program that loads the
operating system.
vi. Once located, the boot program is loaded into memory and executed, which then loads
the kernel of the operating system into RAM.
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vii. The operating system loads system configuration information and the remainder of the
operating system is loaded into RAM and the desktop and the icons display on the screen.
Kernel
The kernel is referred to as a memory resident because it remains in memory while the computer
is running.
It is the core of an operating system responsible for;
I. Managing memory,
II. Managing files and devices,
III. Maintaining the computer‘s clock,
IV. Starting applications and
V. Assigning the computer‘s resources such as printers, scanners, etc.
Conditions under which a computer may fail to boot
In case the hard disk is crash
When there is no installed operating system
When the bootable device is unavailable
System configuration
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This is a process of setting specifications required for a computer or communication device to
properly be usable. That is why it is very important to understand the specifications of a
computer before buying it.
Computer specifications are technical descriptions of the computer's components and
capabilities.
Computer specifications to consider
Components Good Better Best
Processor Intel core i3 Intel core i5 Intel core i7
Memory 4Gb 8GB 16GB
Operating system Windows Xp Windows 7 Windows 10 (64 bits)
Storage 128Gb 256GB 512+GB
Monitor size
Video card Integrated 1-2GB nVidia GeForce 2+GB nVidia GeForce
Warranty 90 days 1 year 3 year +
Resolution 1366x768 1680x1050 1920x1080
How to connect a functioning computer
Before connection, the user must be able to acquire the following parts/peripheral devices;
AC main socket outlets
Uninterruptable power supply
UPS power cable
System unit
System unit power cable
Monitor
Monitor power cable
Mouse
Keyboard
VGA cable
Qn. Explain the procedures for assembling the above devices;
1. Connect a keyboard, mouse & a VGA cable from the monitor to the System unit.
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2. Then connect the power cable of monitor to the power source & then that of the System
unit.
3. Then boot the computer.
Computer programA computer program is a series of instructions that directs a computer how to perform the tasks necessary to process data into information. Programmers write a program and then store the program in a file that a user can execute (run). When a user runs a program, the computer loads the program from a storage medium into memory.It is a list of instructions that tell a computer what to do because everything done on a computer is done by using a computer program. Examples of computer programs include; a web browser like Mozilla Firefox and apple safari, office suite, video games etc.How to start a computer program
Click on the start button Point the cursor to all programs Open a program folder or file by clicking on it or by double clicking on
the program on the desktop.Locating and opening application program
Application preprograms are the software programs used to solve specific end user needs.
Examples of application programs include word processors, database, presentation software, spreadsheets etc.
To open an application program;
Click start All programs Microsoft office
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Click at the desired application program.How to shut down a computer
a) Save all you are doing,b) Close all the running program/ active windows.c) Click on the start buttond) Click turn off computere) Click turn off / shut down
Installing system and application software
Software installation
This is the process of making a program ready for execution.
Types of installation
1. Attended installation: 2. Silent installation: 3. Unintended installation4. Headless installation5. Clean installation6. Network installation
Program installation is the process of setting up of a program on a computer to be able to use it.
A utility responsible for installation of any application software is known as a program installer.
A program installer is a specialized program which automates most of the work required for a
program installation, some installers are specifically made to install the files they contain; other
installers are general-purpose and work by reading the contents of the software package to be
installed.
Operating systems are normally supplied with program installers that run when a new installation
is required. Many programs are supplied with a dedicated installer that must be run in order to set
up the program because the installation process requirements vary for each application.
Installation process
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Open My Computer.
Open the drive that contains the installation files. It may be on a CD or DVD, in that case,
open the D: drive or the letter of the disk drive.
Within the drive that contains the files, locate either a setup or install file. The setup
executable file must have the .exe extension
Alternatively, click Start then Run. In case of windows 7, find run in accessories
In the Run Window, type x:\setup or x:\install where x is the letter of the drive you wish to
start the installation from.
Factors to consider before and when installing a program
Read the manuals for the program or the read me file located in the same directory as the
install commonly contain exact instructions on how to install a program.
Make sure that your computer meets the requirements of the program, game, or utility you
are attempting to install.
After installing or during the installation, a program may need to install other programs, files,
or utilities before it is able to run. If
When installing a program, utility, or game, it is always a good idea first to close or disable
any other programs that are running.
Restart the computer system after installing a new program for it to work well, the computer
may prompt you to reboot the system for the installed program to work.
Hard disk free space
Check on the amount of RAM
Compatibility with the computer basic design
Processor speed
Compatibility with other software
Devices on which software can be installed include;
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Desktops
Smart Phones
I Pads
Laptops
Tablets
Reasons for installing software
In case of the new application package that must be installed in order to run on a
computer
When the previous installed program is corrupted which require its reinstallation
In case one wants to update the old version of the program by installing an update on it
In case a new device is attach to the computer, there is need to install the device driver
software
In case pdf plug-in which is a set of software components that adds specific capabilities
to a large software application.
Reasons for the failure of software to be installed
The software source CD may not be readable. Verify the disk is readable by reading the files
on the drive.
The computer system may not have the system requirements for the software to run, verify
that your computer meets the minimum requirements of the software program.
The software may not be compatible with the computer system. Make sure the program or
utility you are installing is compatible with the version of operating system you have on your
computer.
Most proprietary software requires that a registration code or serial number is entered before
the software is entered. If you lost your number or key or it does not work, you will need to
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contact the developer of the program.
Installing device drives
The device driver is a program that controls a particular type of device that is attached to a
computer system. Modern operating systems are designed with many device drivers. The
operating system will automatically detect any new hardware attached to it and install an
appropriate driver and it will be able to work. However, if you buy a new type of device that the
operating system whose driver was not included in the operating system, you'll have to manually
install the new device driver.
Procedures followed when installing a new device
Open Windows Device Manager (Start>control panel> systems> hardware tab> device
manager
You may need to choose "View" and "Show hidden devices" to find it, or it may be
represented by a yellow question mark if there is no driver for it yet and the computer doesn't
recognize it. The categories may help you find it if Windows knows in general what type of
device it is. For example, if you have plugged in a new keyboard and there's a yellow
question mark under the "Keyboards" category, then you may need to reinstall the keyboard
drivers for it to work.
Once you have verified the Device Manager, reboot the computer.
As the computer is rebooting an “install new hardware” wizard should appear if Windows
detects the new hardware.
Select install for a list or specific location this time and click next. Uncheck "search
removable media" and check includes this location in search.
Click next and it will attempt to install the driver. Once done click next and your new driver
is install. A reboot might be required for the device to work properly.
If Windows does not detect any new hardware, open Control Panel and double-click the Add
hardware (or Add a device) icon to run the hardware detection wizard
Once drivers have been installed reboot.
Upgrading drivers for already installed devices
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Open Windows Device Manager. In the Device Manager locate the device you wish to update
the drivers for.
Right-click the device and click Properties.
In the Properties window click the Driver tab.
Click the Update Driver button.
In the Hardware Update Wizard point Windows to the location of the updated drivers on
your hard disk drive
Once drivers have been installed reboot.
Uninstalling software
Software uninstallation is the deliberate process of removing part or all of a given software from
the computer. A utility used for uninstalling software is an uninstaller.
An uninstaller, also called a de-installer, is utility software which is designed to remove all or
parts of a specific other application software. It is always recommended to use an uninstaller to
uninstall a program.
Reasons for uninstalling software from the computer system;
The software may not be working properly due to corrupt files, or improper installation,
hence the need for a clean reinstallation of the program which requires that the program must
be uninstalled first.
It could be that the software is no longer being used and is unnecessarily taking up valuable
disk space.
The software may be conflicting with other programs installed on the computer.
The software may not be meeting your expectations, that is, it's not functioning as expected.
You may be running out of disk space, therefore you just want to free up some space on your
computer's hard drive.
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It is always necessary to carry out a proper uninstallation through proper program uninstall
procedure instead of merely deleting the program folder and shortcuts
If you are using windows, get to Programs and Features control panel, then choose uninstall
program to properly uninstall the program;
Procedures of uninstalling software from the computer system
Click on the start button
Go to the Control Panel and click
Click on uninstall a program
A list of programs will be displayed
Select the program you want to uninstall and click
Wait until the process of unistallation is done then you click close
Troubleshooting
Troubleshooting is the process of identifying, planning and resolving a problem, error or fault
within a software or computer system. It enables the repair and restoration of a computer or
software when it becomes faulty, unresponsive or acts in an abnormal way.
Troubleshooting is primarily done to keep a system or software in desired condition, specifically
when it encounters or exhibits a problem. It is a systematic approach done within one or more
phases depending on the complexity of a problem.
Typically, the first step involves identifying what the problem is followed by coming up with a
solution to counteract the problem and then implementing that solution. However, there can be
more than one reason for the problem, which will require a more complex solution. An
individual troubleshooting such a problem might test for different solutions to eliminate the
problem or fault.
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Hardware troubleshooting is the process of reviewing, diagnosing and identifying operational
or technical problems within a hardware device or equipment. It aims to resolve physical and/or
logical problems and issues within a computing hardware. Hardware troubleshooting is done by
hardware or technical support technician.
Hardware troubleshooting processes primarily aim to resolve computer hardware problems using
a systematic approach.
The process starts by first identifying the problem and finding different issues that can cause
such a problem and eventually leading to implementing a solution or alternative. Hardware
troubleshooting is generally done on hardware equipment installed within a computer, server,
laptop or related device.
The various troubleshooting technique used in computer management includes;
a) Use of diagnostic utility
b) Scan disk utility
c) Starting the computer from an external device
Processes within hardware troubleshooting:
Removing, repairing and replacing faulty RAM, hard disk or video/graphic card.
Cleaning dusts from RAM and Video carts slot/ports and from cooling fan.
Tightening cable and jumpers on motherboard and/or components.
Software related hardware problems such as device driver update or installation.
How to troubleshoot a computer
Click on the start button
Click the control panel
Under system and security click find and fix problems
Troubleshooting Processes
Identification of the malfunctions within the system
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Generate possible causes of the malfunctions and eliminate them
Confirm that the solutions restore the process to its working state
Troubleshooting techniques
1) Isolating the problem by finding out if it is software or hardware related, if it is hardware
start with the obvious such as power and loose connections then run diagnostic test.
2) Researching for the ideas related to the problems which may involves asking friend for
advice or referring to reference books or searching from the internet
Common computer problems
a. Power button fails to start the computer.b. Application program running slowlyc. The computer runs slowlyd. Freezes of the computere. Failure of the sound to workf. The mouse or key board stops working
Freezing /hanging up.
This is a situation where the computer becomes completely unresponsive to the commands. When this happens, the user is unable to click anywhere on the screen, open or close any application or access shut down options.
If this happens; Warm boot the computer by pressing Ctrl + Alt + delete keys simultaneously.
Causes of system freezing
1. Overloading the machine with a lot of data and information.2. Multitasking (running too many programs at the same time.3. Virus attack4. When the running program has encountered a problem.5. High traffic in case of a networked system.
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6. Low RAM7. Aging hardware8. Dust particles in the system unit9. Installing incompatible software on the machine.10. Corrupted operating system11. Entering too many commands at the same time.
TOPIC 11: DATA COMMUNICATION & NETWORKING
Definition of Data communication
Data communication is the process of transferring data, instructions and information from one
computer to another computer.
Elements of data communication
A sending device
Message
A communication device
A communications channel
Protocol
Communications software
A receiving device
A sending device;
A sending device is a device that initiates an instruction to transmit data, information, or
instructions. It can be a computer system, a terminal, a cellular telephone, a GPS receiver, an
Internet- enabled PDA, or another device that originates the message.
Message
This is the data/content/information to be transmitted over a transmission medium. The message
is usually in a discrete form.
A communication device;
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Is a device that connects the communications channel to a sending device by converting the data,
instruction or information from the sending device into signals that can be carried by a
communications channel; It can be a modem, repeater, switch, router, gateway etc.
A communications channel/medium Also known as communication links or Data links a
communication channel is a medium over which Data travels/is transmitted from one computer
(device) to another. It is a path over which the signals are sent either physically (cables) of
wireless waves. It can be a standard telephone line.
Protocol
This is a set of rules and procedures for exchanging information among computer
device on a network.
A receiving device;
It is the device that accepts the transmitted signals from the sending device. They include
computers, fax machine, digital cameras, cellular telephone, smart phone, PDA, Internet
appliances, and Web-enabled devices.
Communications software;
This software consists of programs that manage the transmission of data, instructions and
information between the sending and receiving computers. It controls and manages the activities
and functions of the communications network.
Importance of computer communication
It facilitates communication over distant areas with help of email, chat etc services
It allows sharing of resources such as printers, routers, storage devices etc
It is reliable
It ensures cost effectiveness in the usage of resources in an organization.
It ensure security of data by putting in place administrative controls over the network
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It enables distribution of processing facilities
Limitations of computer communication
There is increased risk of data corruption
Data and information transmitted by computer communication technology is vulnerable
to threats
The initial cost of buying communication devices are expensive and costly to maintain
There is great risk of malware infections such as viruses and worms
Computer communication offer worries like hardware and software failure and
troubleshooting
Definition of data communication tools
These are tools that enable the user to emulate and test the networks.
Types of electronic data communication tools
Mobile phones
Computers
Internet
Social network
Mobile phones
Wireless phones are the most dominant form of communication in the world. Text messaging is now
rampant because of the advent of smart phones which allows the mobile phones to have personal
computer functionality of sending large pictures and video files.
Computers
A computer is a multipurpose, automatic and electronic device which allows the user to input data, store
data and information, process data and output information for the future reference.
It is an electronic and automatic machine made up of electronic and electromechanical device which
manipulates and processes data.
Internet
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Internet is an International/global interconnection of computer networks It is a global network where all
LANs (both big and small) worldwide are interlinked.
Social network
Social medium enable instant interactions among user, who can communicate directly through twitter,
face book, what saps etc.
Services offered by data communication tools
Voicemail
Fax
E –mail
Bulletin Board System (BBS)
Instant messaging (IM)
Chat room
Newsgroups (Discussion groups)
Internet telephony
Videoconferencing
Telecommuting
Groupware
Skype
Voicemail
This functions like an answering machine. It allows a caller to leave a voice message which is
stored in a voice mail box for the caller party. The called party can listen to the message, add
comments to the message and reply or forward the message to another mail box in the voice mail
system.
Fax
A facsimile (fax) machine is a device that transmits and receives documents over telephone lines.
Sent or received documents are called faxes. Fax capability can be added to a computer using a
faxmodem.
E –mail
Email is a transmission of messages via the internet and users can access it from countless
devices including cell phones. Email is virtually instant, much like modern communication
modes.
Bulletin Board System (BBS)
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It is a computer that maintains centralized collections of electronic messages. They are declining
because of the emerging of internet which can serve the same purpose.
Instant messaging (IM)
Instant messaging is a real time communications service that notifies a user when one or more
people are online and then allows the user to exchange messages or files with them.
Chat room
Chart room is a location on an internet server that permits users to chat with each other by typing
lines of text on the computer.
Newsgroups (Discussion groups)
It is an online area where users conduct written discussions about a particular subject.
Internet telephony
It is also called a Voice over IP (VoIP). It is a web based telephone that allows a user to talk to
others for just the cost of the internet connection. A microphone, sound card and special internet
telephony software are required for conducting internet telephony.
Videoconferencing
It is a meeting between two or more geographically separated people who use a network or the
internet to transmit audio and video data.
Groupware
It is a software application that helps groups of people to work together and share information
over a network. It enables members of a workgroup to communicate, manage projects, schedule
meetings and make group discussions.
Skype
This service allows users to communicate with peers by voice using a microphone, video by
using a webcam and instant messaging over the internet.
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Telecommuting
Telecommuting is a work arrangement in which employees work away from the standard
workplace of a company, but communicate with the office using some kind of communications
technology
Advantages of telecommuting
Reduces time and expenses for travelling to and fro work.
Eliminated travelling during bad weather conditions
Allows flexibility in the work schedule
Reduces air pollution by vehicles driven to and fro work
Employers reduce costs due to less office space and furniture required.
Favors the disabled employees
Disadvantages of telecommuting
Reduces human face – to – face interactions among the working staff
If any device of the communications system fails, the work has to stop.
Leisure time at home may be replaced by work.
There is less security over the company’s information.
Global positioning (GPS)
It consists of one or more earth based receivers that accept and analyze signals sent by satellites
in order to determine the receiver‘s geographical location.
Uses of GPS
To locate a person or an object
To find the best route between two points
Monitor the movement of a person or object.
Create a map
To get weather information
Used by cars and ships to provide directions.
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Difference between electronic and manual data communication tools
Electronic Manual
Require payment for the service Payment is not required
It is very costly to maintain They are very cheap to maintain
Computers are linked for easy
communication.
Drums are used as the most musical tool.
The invention of MMS, SMS, and EMS has
made communication more adaptive, and
motivate to both senders and receives.
A single communication tool such as a drum
has many techniques that enabled sound
communication
Mobile phones as a communication tools
have resulted into fast pacing communication
session.
Several drums, other than timpani drums can
be arranged together to create a drum kit.
Email for education purpose as a
communication tool has help teachers, at the
elementary, secondary level and parents to
communicate on line openly.
Massagers or courier carry messages from
the source to the recipient
Forms (modes) of Data transmission (Communication)
Data transmission/digital transmission/ digital communications is the physical transfer of data
over a point-to-point or point-to-multipoint communication channels. Examples of such channels
are copper wires, optical fibers, wireless communication channels, and computer buses.
Data is transmitted over networks using signals, which are transformed, or encoded, by
computers into the voice, video, graphics, and/or the print we see on our computer screens.
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A signal is a series of electrical or radio waves which are sent to a radio or television in order to
produce a sound, picture or message. The signals used by computers to transmit data are either
digital or analog
Analog signals are continuous signals that vary in strength. Sound is an example of an analog
signal.
Digital signals are discrete/ discontinuous. Either there is a signal or there isn't a signal. Discrete
signals are represented by on (1) and off (0) pulses.
Modulation and Demodulation of Signal
Modulation refers to the process of converting digital signals into analog form so that data can
be sent over the phone line.
Demodulation is the process of converting the analog signals back into digital form so that they
can be processed by the receiving computer.
Notice; A modem is a hardware that performs modulation and demodulation processes.
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Examples of data transmission (Communication) forms (modes)
Serial transmission
Serial transmission is the sequential transmission of one bit of signal at a time sent over a single
wire. Low data transfer rates are possible, but can be used to transfer data over longer distances.
Parallel transmission
Parallel transmission is the simultaneous transmission of the signal elements of a character or
other entity of data over two or more separate paths. Multiple electrical wires are used which can
transmit multiple bits simultaneously, which allows for higher data transfer rates than can be
achieved with serial transmission
Asynchronous Data transmission
Transmission where each group of digital or analog signals making up the code for one character
is separated and individually wrapped with a start BIT and a stop BIT and an error check BIT.
Asynchronous transmission is relatively slow because of the extra bits that must be sent with the
data bits for each character.
Synchronous Data transmission
This is the transmission where characters are sent as blocks of signals with header and trailer
bytes at the beginning and end of the block. Synchronous transmission is faster because
characters are sent as blocks; it is therefore used to transmit large volume of data at high speed.
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DIRECTION OF DATA TRANSMISSION
Simplex transmission
This is a type of transmission where data flow in only one direction from the sending device to
the receiving device.
It is used only when the sending device doesn‘t require a response from the receiving device. It
is applied in security alarms and fire alarms that contain sensors, Radio and Television
broadcast, communication between a mouse and computer.
Half duplex
This type of transmission allows data to flow in either direction from the sending device to the
receiving device and back but not at the same time.
An example of a half-duplex system is a two-party system such as a walkie-talkie. It is used in
radio calls, ATM machines, Fax machines, credit card verification systems, etc,
Full duplex
This type of transmission allows data to flow in both directions at the same time for instance
modern telephone system; the sender can be able to talk while listening to the receiver on the
other side. . E.g. Land-line and Cell telephone networks are full-duplex, since they allow
both callers to speak and be heard at the same time
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Point to point transmission
A point-to-point connection refers to a communications connection between two nodes or
endpoints.
Multi-Drop transmission
Multi –drop transmission is a transmission bus in which all components are connected to the
electrical circuit. A process of arbitration determines which device sends information at any
point. The other devices listen for the data they are intended to receive. There are both physical
(cable or wired) media, and wireless media.
Definition of data transmission media
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This is a communication channel or path over which the data signals are sent from the source to
the destination.
Types of data transmission media
There are two types of transmission media, i.e.
Physical (Guided/bounded) transmission media
Wireless (Unguided/Unbounded) transmission media
Data Transmission media
Physical/Guided/Bounded Transmission
media
Wireless/Unguided/Unbounded transmission
media
Twisted pair Cables Microwaves
Unshielded twisted pair cable Satellites
Shielded twisted pair cable Infrared
Coaxial cables Bluetooth technology
Fiber Optic Cables Wi-Fi technology
This is a kind of media which uses wires, cables or other tangible material to send
communications signals. These include twisted pair cables, coaxial, and optical fiber cables.
Twisted pair cable
Twisted pair cables are types of cables in which two conductors of a single circuit are twisted
together for the purposes of improving electromagnetic compatibility and to reduce
electromagnetic radiation, crosstalk between neighboring pairs and rejection of
external electromagnetic interference.
Types of twisted pair cable
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Shielded twisted pair cable (STP)
Shielded twisted pair cable is a type of copper telephone wiring in which each of the two copper
wires that are twisted together are coated with an insulating coating that functions as a ground for
the wires. The extra covering in shielded twisted pair wiring protects the transmission line
from electromagnetic interference leaking into or out of the cable.
Unshielded twisted pair cable (UTP)
Unshielded Twisted Pair able is a pair of wires without a metal wrapper for shielding noise that
are twisted around each other to minimize interference.
Advantages of twisted pair cables
They are relatively cheap to use because its cost per unit length is low.
They are convenient to use because they are small in size.
They are easy to install because of their flexibility it is easily strung around the room or
wall.
Shielded twisted pair has a foil shielding to help provide a more reliable data
communication.
TP is easy to terminate
It is inexpensive and easy to install.
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UTP connector (RJ 45)RJ stands for “registered jack”
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The Disadvantages of twisted pair cables
Used over a short distance, usually less than 100 meters
Twisted pair’s susceptibility (prone) to the electromagnetic interference which leads to
signal loss
They are easily damaged. Especial the UTP
They are low frequency cables. So they are not suitable for transmission of very high
frequency signals like cable TV, TV antenna and radio antenna signals
N.B The basic difference between STP and UTP is that Shielded twisted pair is a twisted pair
cable enclosed in foil or mesh shield that protects against electromagnetic interference
meanwhile Unshielded twisted pair is a cable with wires that are twisted together to reduce noise
and crosstalk.
And the deference between a wire and a cable is that a wire is a single conductor (material most
commonly being copper or aluminum) while cable is two or more insulated wires wrapped in
one jacket.
Coaxial cable;
This is an electrical cable connected over long distances that consists of a single copper wire
surrounded by three insulating layers i.e. an insulating material, a braided metal and a plastic
outer coating. Coaxial cable is insulated more heavily than twisted-pair cable, and thus is not as
susceptible to noise.
Features of coaxial cable
Both conductors share a common center axial, hence the term "co-axial"
It has a high bandwidth
It is highly resistant to signal interference
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It is used for long distance (300-600 meters)
It is quite bulky and sometimes difficult to install
The most common type of connector used with coaxial cables is the BNC connector
It has higher installation costs
Coaxial is prone to lightning strikes which damage the cables or equipment on which it is
connected.
It is more expensive than twisted pair cables
It is not flexible
Advantages of coaxial cables
It has a high bandwidth capacity
It can be used for long distances between 300-600 meters
It is very effective at carrying many analog signals
It is resistance to signal interference because of its protection shield
Disadvantages of coaxial cables
It is not flexible
It is quite bulky and sometimes difficult to install
It is more expensive that twisted pair cables
It has high installation cost
It is prone to lightening strikes which can damage the cables.
Fiber – optic cable;
A fiber optic cable is a cable that contains hundreds of thin strands/fibers (tiny threads) covered
by insulated glass coated in plastic that use pulses of light to transmit data or signals .The
protective coating is to protect the fibers from heat, cold, electromagnetic interference from other
types of wiring, as well as some protection from ultraviolet rays from the sun. Fiber optics allow
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for a much faster data transmission than standard copper wires, because they have a much
higher bandwidth.
Advantages of fiber optic cables over wired cables
Carry more signals that wired cables.
They transmit data faster.
They are less susceptible to noise from other devices
Has a better security for signals during transmission
They are small in size and lighter that wired cables.
Disadvantages of fiber optic cables over wired cables
They are more expensive
They are difficult to install and modify
They are delicate.
It is difficult o add additional nodes on the network
It is very complex to configure
Wireless (unguided) transmission media
This is a kind of media that sends communications signals through the air or space using radio,
microwave and infrared signals. Wireless telecommunications technologies transport digital
communications without wires between communications devices. They are used when it is
inconvenient, impractical, or impossible to install cables.
The transmission in wireless technology is facilitated by the use of antenna and receiver/aerials.
Antenna is an electronic conductor use either for radiating electromagnetic energy or for
collecting electromagnetic energy.
Categories of wireless transmission media
Broadcast radio
Bluetooth,
Microwaves
Communications satellite
Wi-Fi
Cellular radio
Infrared (IR)
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Broadcast radio
Radio broadcast is a wireless transmission medium that uses radio waves through the air to send
transmissions over long distances to a large audience who will listen to the transmission through
a radio. Radio broadcast can be expanded by examining radio waves, radio transmitters and
receivers.
A transmitter is needed to send the broadcast radio signal. To receive the broadcast radio signal,
a receiver with an antenna that is located in the range of the signal is needed.
Broadcast radio is slower and more susceptible to noise than physical transmission media but it
provides flexibility and portability.
Advantages of Broadcast Radio
1. Radio covers huge population with a single message.
2. Radio can be enjoyed anywhere be it at home, in office or while driving car.
3. It is less expensive
4. You can advertise your product on radio and the rate of advertisement is usually lower than other
medium of communication.
5. Important information or news can be easily spread on radio.
6. For local market radio is one of the powerful medium of communication.
7. It utilizes modulation schemes such as AM and FM to leverage advantages of both of them.
8. It trains audience to be good listeners.
Disadvantages of broadcast radio
1. It favors only audio medium for communication.
2. It does not favors deaf people
3. It is greatly affected by bad weather
4. You need to adjust frequency properly.
5. Less and limited radio channels are available compared to other communication medium.
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Bluetooth,
This is a short range wireless technology standard for exchanging data over short distances for
fixed and mobile devices. In order for devices to communicate, they must be able to understand
the blue tooth rules (protocols).
Advantages of Bluetooth Technology
Connection establishment is very quick because users only need to pair the Bluetooth
personal area network connection between two devices.
It has low power consumption.
It can pass through walls.
It has better range than Infrared communication.
There is no issue of interoperability among different Bluetooth vendor products.
It is used for voice and data transfer.
Bluetooth technology is adopted in many products such as head set, in car system,
printer, web cam, GPS system, keyboard and mouse.
Due to availability of Bluetooth headphones, calls can be taken on phone even while
driving and doing some other activity simultaneously.
Bluetooth devices are available at very cheap cost.
It has less interference compare to other wireless technologies
Easy to install
It makes connecting to different devices convenient
Disadvantages of Bluetooth Technology
It can easily be hacked into by intruders
If installed on a cell phone it is prone to receiving cell phone viruses
It only allows short range communication between devices
It can only connect two devices at once
It can lose connection in certain conditions
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The bandwidth is lower compare to Wi-Fi.
Battery usage is more compare to the condition when Bluetooth is powered OFF
Microwaves
These are high-frequency radio waves that are sent through the atmosphere and space. They
provide a high speed signal transmission by receiving signals amplifies it and transmits it to the
receiving devices or retransmits it to the next microwave transmission tower. Microwave
transmission involves sending signals from one microwave station to another thus called fixed
wireless.
A microwave station is an earth-based reflective dish that contains the antenna, transceivers, and
other equipment necessary for microwave communications.
Microwaves transmit signals in a straight line with no obstructions between microwave antennas.
To avoid possible obstructions, such as buildings or mountains, microwave must be set on the
tops of buildings, towers, or mountains.
Advantages of microwaves
It is difficult to implement lumped components such as resistors, inductors and
capacitors at microwave frequencies.
Microwave communication is limited to line of sight mode only, where loses that we
face in the ground-wave and sky-wave propagations are absent or minimum
Antennas required at microwave frequencies are much smaller in size than those used at
lower frequencies hence low losses of signals
Their comparatively higher frequencies allow broadband width and high data flow
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Disadvantages of microwaves
Microwave frequencies travel only in straight line path which are limited by horizon
hence difficult to propagate.
Microwave transmission towers are complex in construction, and are highly expensive.
Microwave systems do not pass through solid objects. This can be problematic in cities
with a lot of tall buildings or mountainous regions if you want to send a signal from one
end of the city to the other.
Microwave is subjected to electromagnetic interferences such as Electric motors, electric
power transmission lines that disrupts microwave communication
Microwave is also degraded by heavy wind turbines and moisture in the atmosphere such
as snow, heavy rain and fog in a phenomenon known as rain fade.
Microwave can be exposed to electronic eavesdropping
Applications of microwaves
Broadcasting and telecommunication
To detect the range, speed, and other characteristics of remote objects (Radar technology
is a technology that uses radio waves to find the position of objects which cannot be seen)
Radio astronomy
In navigation especially global navigation microwave systems (GNSS)
Heating and power application e.g. microwave ovens
Communications satellite; Satellites are communication devices stationed in space and use
microwave radio as their telecommunications medium to communicate with the earth based
communication facilities. These earth-based stations often are microwave station.
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The above flow chart shows the general structure of a satellite communications system. A
Satellite in space links many earth communication facilities. The user is connected to the earth
station through the terrestrial network with various configurations including a telephone switch
or a dedicated link to the earth station. The signal generated by the user is processed and
transmitted from the earth station to the satellite.
Transmission from an earth-based station to a satellite is called uplink meanwhile transmission
from a satellite to an earth-based station is downlink. The uplink frequencies are kept different
from the downlink frequencies in order to avoid interference.
N.B Terrestrial systems are television channels which are broadcast from stations on the ground
and do not use satellites
Applications of satellites
They are used in applications such as;
Air navigation,
Television and radio broadcasts,
Weather forecasting,
Video conferencing,
Paging,
Global positioning systems,
Internet connections etc
Advantages of satellites communication
They receive and broadcast data/signals over larger geographical regions.
They sent a lot of data/ signals simultaneously.
They allow high quality broadband communication across continents
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Satellite communication allows easily establishment of mobile communication
Satellite communication has high bandwidth.
Satellite communications are economical compared with terrestrial communication,
particularly for thin traffic remote areas and where long distances are involved.
They are cheaper over long distances.
Satellite communications allow additional connection on a network; so long as terrestrial
system has the ground-based equipments.
They allow earth Station to be removed from a location and reinstalled somewhere else.
Satellite communications allow users to have control over their own network.
Disadvantages of satellites
It takes long and time consuming to propagate satellite tower
The time delayed in propagation reduces the efficiency of communication satellite in data
transmission.
The initial cost is very expensive and costly
They are subjected to interference by phenomenon
Repair of the satellite is almost impossible, once it has been launched
The infrastructure needed to access satellite communications is also expensive.
Wi-Fi
Wi-Fi is a short form for "wireless fidelity," it is a wireless networking technology that allows
electronic devices to exchange data using radio waves over a computer network including high-
speed wireless Internet and network connections.
Devices that use Wi-Fi such as personal computer, video game console, and smart phones,
tablets, I-pads or digital audio player can connect to a network resource such as the internet via a
warless network access point.
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Advantages of Wi-Fi
It is easy to add or move wifi clients or wifi stations to the wifi network created by AP
(Access Point).
Installation is very quick and easy. It does not require technical knowledge of wifi system
and its protocols.
Access to the wifi network can be availed from anywhere within the wifi AP (Access
point) coverage range.
It is easy to integrate wifi functionality in the mobile computing devices
Wi-Fi protected access encryption is considered secure
Different competitive brands of access points and client network inter-operate at a basic
level of service.
Manufacturers are building wireless network adapter into most laptops leading to the
reduction in the price of the chipsets for Wi-Fi
Wi-Fi allows cheaper deployment of local area network.
Disadvantages of Wi-Fi
Wi-Fi networks have limited range, and this range varies with frequency band
Devices that uses Wi-Fi has high power consumption
Wi-Fi connections can be disrupted or the internet speed lowered by having other devices
in the same area.
Wi-Fi is less secured than wired connections for instance Ethernet because an intruder
does not need physical connections.
The practical range of Wi-Fi does not favor mobile devices.
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Cellular radio
Is a form of broadcast radio that is used widely for mobile communications, specifically wireless
modems and cellular phones. Cellular transmission uses radio waves; therefore, it is possible for
people with special receivers to listen to cell phone conversations.
Advantages of cellular radio systems
They have high user capacity that is the smaller the size of the cell, the number of
concurrent users. So huge cells do not allow for more concurrent users
They transmit less power because of the cells are smaller in size
For huge cells there are a number of interfering signals, while for small cells there
is limited interference only.
As cellular systems are decentralized, they are more robust against the failure of
single components.
Disadvantages of cellular radio systems
Small cells require a complex infrastructure to connect all base station. The
infrastructure required includes switches for call forwarding, location registers etc.
The mobile station has to perform a handover when changing from one cell to
another very frequently.
To avoid interference, frequency spectrum should be distributed properly with a
very less range of frequency spectrum.
Infrared (IR)
Is a wireless transmission media that transmits signals across relatively short distances to
transmit data between personal devices using infrared light waves for instance a computer and a
cell phone.
These devices have an IrDA port
that enables the transfer of data from
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one device to another using infrared light waves. Infrared transmission can be used to establish a
wireless network with the advantage that devices can be moved, removed, and installed without
expensive wiring and network connections.
Advantages of IrDA (Infrared)
The devices are very cheap.
The devices are compact, light weight and consume low power.
The technology based devices are easy to use.
It is non interfering from RF waves.
They are more secure compare to RF technologies.
Disadvantages of IrDA (Infrared)
The area for data transfer is very less.
They are used for very short distance applications only.
Due to line of sight communication is blocked by obstacles.
They allow only one device at a time
They require both transmitter and receiver to be in line of sight.
Devices cannot move around while transmission is in progress.
Terminologies useful used in data transmission
Baseband transmission media is the kind of media that can only transmit one signal at a time.
Broadband transmission media is the kind of transmission media that can transmit multiple
signals simultaneously.
Latency is the time it takes a signal to travel from one location to another on a network.
Attenuation is the process by which signals undergo reduction in its strength as it travels
over long distances.
Throughput refers to the amount of data to be transferred from one location to another in a
given amount of time.
Bandwidth is the difference between high frequency and low frequency
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Crosstalk is a signal transmission issue that causes a disruption in another circuit or channel.
Advantages of using wireless technologies
Wireless technologies overcome inconvenience of using too many wires for
communication.
Wireless technology makes it easy to set up temporary network installations
Wireless increase flexibility and mobility at the work place because works can sit
anywhere with their computers without being limited by the extent of cable connections.
Fast data transfer rates are possible where there are no environmental obstacles
Wireless technology is appropriate to use in places where cabling is practically
impossible.
Disadvantages of using wireless technologies
They are slower than LANs using cabling
They are prone to electrical interference from light and radio
They are subjected to obstruction especially walls
Wireless access point and Wi-Fi technology in general have limited range that is signal
strength decrease as the range increase.
Poor security of data on a wireless network, outsider can easily log on an unsecured
wireless network.
Factors to consider when choosing a communication/transmission media
Speed of data transmission
Cost of transmission media
Installation cost
Data security
Country/company policy
Availability of the communication media in the market
Size of the network
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Implications of using data communication services
The integration of voice, video and data onto the same networks greatly simplify
networks and enable anyone to access any media at any point
Data communication services bring about standards by ensuring that hardware and
software produced by different vendors can work together.
Successful users of data communication services can gain significant competitive
advantage in the market place since they easily access their partners through faster
communication.
Future trends pervasive networking will change how and where we work and with whom
we do business.
Computer network
A Computer network is the interconnection of two or more computers and other devices for
purposes of sharing information and resources. The computers on a network must be linked by a
medium such as cables, a wireless device or a telecommunications system in order to exchange
data.
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Why a computer Network?
Purpose of computer networking
To allow users to share information,
To enable sharing of software’s
To allow the users to share resources such as printers, modems, storage devices etc
To enable communication between computers users through tools like e-mail.
To enable data communication I.e. transmission of electronic content over a given
medium
To ensure security of data by putting in place administrative controls over the network
To share databases
Basic requirements for setting up a computer network
These are elements/components that make up a computer network to ensure that there is
communication between them. Among them include;
1. Computers/clients/workstations
2. Network hardware devices
3. Transmission or communication media/channels
4. Network software
5. Server
1. Computers/clients/workstations
These are other computer on the network except the server that sends request and receive
responses from the server
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2. Network hardware devices
These are devices that handle the movement of data in a computer network.
Modems
Router
Hub
Switch
Gateway
Bridge
Repeaters
Network interface cards
Multiplexer,
A modem
The word "modem" is a contraction of the words modulator and demodulator i.e. Modulation
and Demodulation.
Modulation is the process of converting digital signals into analog signals while Demodulation
is the process of converting analog signals into digital signals.
A modem modulates outgoing digital signals from a computer or other digital device to analog
signals for a telephone line and demodulates the incoming analog signal and converts it to a
digital signal for the digital device.
Therefore a modem is a communication device that converts between analog and digital signals.
There are six types of modems
Dial – up modem
PC Card Modem
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ISDN (Integrated Services Digital Network) and DSL(Digital Subscriber Lines)modems
Wireless modem
Cable modem
Fax modem
Dial-up modem
A dial-up modem usually is in the form of an adapter card that one inserts in an expansion slot
on a computer’s motherboard. This is the communications device that performs the function of
modulation/demodulation
Dial-up modem automatically dials telephone numbers, originate message sending,
and answer incoming calls and messages.
Both the sending and receiving ends of a standard telephone line must have a dial-up
modem for data transmission to occur.
PC Card modem
This is normally inserted into a PC Card slot of notebook and other mobile computers which
don‘t have built – in modems. The PC Card modem attaches to a telephone outlet with a
standard telephone cord.
Mobile users without access to a telephone outlet also can use a special cable to attach the PC
Card modem to a cellular telephone, thus enabling them to transmit data over a cellular
telephone.
ISDN (Integrated Services Digital Network) and DSL (Digital Subscriber Lines) modems
A DSL or ISDN modem is a communication device that sends digital data and information
from a computer to a DSL or ISDN line and receives digital data and information from a DSL
or ISDN line. ISDN and DSL modems usually are external devices, in which one end connects
to the telephone line and the other end connects to a port on the system unit. Most include built
in connectivity.
A DSL Modem
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Wireless modem
A wireless modem is a communication device that converts digital data into radio signals and
back.
Fax modem
A fax modem is a communication device that enables a computer to transmit and receive
documents as faxes.
Router
Is an intelligent communications device that sends communications traffic to the appropriate
network using the fastest available path
Hub/concentrator
A hub is a device that connects multiple devices to the network and its function is to send and
receive signals along the network between the devices connected to it by broadcasting the data to
all the devices/computers. It serves as a central meeting place for cables from computers, servers
and peripherals on the network. The entire network shuts down if there is a problem on a hub
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Switch
A switch is a high-speed device that maintains a bridging table, keeping track of which hardware
addresses are located on which network segment. It maps the internet protocol (IP) address with
the Media Access Control (MAC) address of the LAN card. It sends the data packets only to the
destined computer. Switches are used in the LAN, MAN and WAN.
Gateway
A gateway is a communication device that consist of a combination of hardware and software
that connects networks that use different protocols technologies by performing the required
protocol conversions
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Bridge
A bridge is a device that links two local area networks that use the same address method or
protocol. It accepts all packets from each network addressed to devices on the other, buffers
them, and retransmits them to the other network.
Repeater
A repeater is a communication device that accepts a signal from a transmission medium,
amplifies it, and retransmits it over the medium in order to overcome attenuation. Hence
repeaters are needed over the medium to boost up these signals
N.B Attenuation is the process by which signals undergo reduction in its strength as it
travels over long distances.
Network interface cards (NIC) or LAN Adapter
A network interface card is an electronic communication device or an expansion card that
enables other devices on a computer to connect to a network.
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Some NICs are built-in on the motherboard while others are built on a circuit board fitting into
an expansion slot inside the computer. N.B The Type of NIC determines the speed and
performance of a network.
There are three common NICs: Ethernet cards, Local Talk connectors, Token Ring cards
Multiplexer
Multiplexer is a communication device that combines two or more input signals from various
devices into a single stream of data and then transmits it over a single transmission medium.
3. Transmission or communication (Network) media/channels
Transmission or communication (Network) media/channels is also known as communication
links or Data links. It is a medium over which Data travels/ transmitted from one computer
(device) to another.
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4. Network software
Network software’s are Communication programs that are used in combination with network
devices to enable transmission of data between network terminals. They have features such as
Dialing, file transfer, internet access and others.
There are two categories of network software’s; Network operating system (NOS) and Network
protocols.
Network Operating System (NOS)
A network operating system is a supervisory software program that resides on the server and
controls a network by;
(i) Defining who can use the network
(ii) Determining how information is shared
(iii) Controlling access by multiple users to network resources such as files and hard ware
(iv) Provides for certain administrative functions, including security
Examples of common NOS;
Novell Netware
Microsoft Windows NT,
windows server*,
AppleShare,
UNIX,
Linux
Network operating system carries out the following administration activities:
1. Managing the Security of the network by providing Security features such as authentication,
authorization, logon restrictions and access control.
2. File management.
3. Providing basic operating system features such as support for processors, protocols, automatic
hardware detection and supporting multi-processing of applications.
4. Providing name and directory services.
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5. Coordinates the activities of multiple computers across a network.
6. Providing file, print, web services, and back-up and replication services.
Network protocols
A protocol is a set of rules and procedure (standard) for connection and data transfer between
devices on a network. Protocols control all aspects of data exchange, which include the
following:
How the physical network is built.
How devices connect to the network.
How the data is formatted for transmission.
How that data is sent/transmitted.
How to deal with errors in data transfer.
The Protocols are created and maintained by a number of different organizations and committees
including:
Institute of Electrical and Electronic Engineers (IEEE),
American National Standards Institute (ANSI),
Telecommunications Industry Association (TIA),
Electronic Industries Alliance (EIA)
International Telecommunications Union (ITU).
Functions of protocol in a communications network
Identifying each device in the communication path
Securing the attention of the other device
Verifying correct receipt of the transmitted message
Determining that a message requires retransmission if it is incomplete or has errors.
Performing recovery when errors occur
Commonly used protocols
TCP/IP-transmission control protocol/Internet protocol.
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HTTP- Hypertext transfer protocol
FTP- file transfer protocol.
POP- post office protocol
SMTP-Simple mail transfer protocol
IPX/SPX-stands for Internetwork Packet Exchange/Sequenced Packet Exchange. IPX and
SPX are networking protocols used primarily on networks using the Novell NetWare
operating systems
NETBEUI-(NetBIOS Extended User Interface) is a new, extended version of NetBIOS, the
program that lets computers communicates within a local area network. it does not support
the routing of messages to other networks,
Telnet (Telecommunication Network) for Remote access between computers
IMAP; Internet Message Access Protocol.
The Point-to-Point Protocol (PPP) which is a data link protocol commonly used in
establishing a direct connection between two networking nodes.
5. Server
A server is a computer that runs software that enables it to serve specific requests from other
computer (clients).
Implications of using computer networks
Positive implications (advantages)
It facilitates easy communication for instance through electronic mail.
Allow users to log on and access their work from any workstation on the network
Computer network provides rapid method of sharing files instead of using movable disks.
Computer networks enable workgroup computing
It allows software to be upgraded easily on the network since it is done at ago on the
server.
It enable online learning and collaborative research
Computer network allows sharing of data and information stored on any other computer
on the network.
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It reduces on cost by sharing hardwires and software’s among the network since one
device is jointly used in the network instead of installing a hardware and a software to
each computer.
Negative implications (disadvantages)
Initial cost of installing a network on Cables, network cards, and software are expensive,
and the installation may require the services of a technician.
Networks require Administrative Time and expertise for Proper maintenance of a
network which leads to additional cost.
Time can be wasted on social networks instead of doing meaningful work.
The entire networker fails if the server crashes, When this happens, the entire
organization loses access to necessary programs and files.
There is increased risk of data corruption, since many users will be using the system to
access the same documents, some of whom may be careless or deliberately tamper with
it.
Increased exposure to hackers which puts private data at risk
There is a greater risk from viruses, because they are easily spread between the
computers that are part of the LAN.
A break in the communication channel can stop the entire network.
Different types of computer network
Communication networks can be grouped into the following categories based on the
geographical locations of its computer terminals;
LOCAL AREA networks (LANs)
Metropolitan area networks (MAN)
WIDE AREA networks (WANs)
Wireless local area network (WLAN)
Wireless Wide area network (WWAN)
International network (Internet)
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Local Area Network (LAN)
A local area network is a network that connects computers and other devices within a small
geographical area such as a room or a building, home a school or a computer laboratory. The
devices are interconnected using a medium such as cables or a wireless medium
Types /categories of local Area Networks (Network Models or architectures)
There are two categories of local area network models or architectures;
Peer-to-peer networks
Clients-server networks
This is an interconnected group of equal computers where there is no hierarchy among them,
each computer acts as both a client and a server to others on the network.
Peer to peer Configurations
Characteristics of peer to peer network
All computers access resources equally.
Each computer stores files on its own storage devices.
Each computer has its own network operating system and application software.
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It normally connects less than 10 computers together.
It is suitable for home and small scale business users
Each computer has resources it shares with others on the network.
Advantages of a peer to peer network
It is very simple/easy to setup
It is inexpensive to maintain
Do not require additional specialized network administration software
Do not require a dedicated network administrator.
Disadvantages of a peer to peer network
They are not easy to administer
Each user must be trained to perform administrative tasks
Reduced performance because all the devices share resources equally
It doesn‘t allow remote installation of software
It lacks security due to absence of a server.
It’s not appropriate for big networks (cannot be used for big networks).
Clients-server networks
This is a type of local area network that consists of a central computer (the server) on which
other computers (clients) are connected. The central computer providing services to client
computers
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Characteristics of client server network
It can connect more than 10 computers
It requires a network administrator to manage the network
The server controls communication and shared network resources.
NETWORK SERVER
A server (Network server) is a computer on a network that controls and manages the network
resources, making them available to its clients (computers connected to it).
Client Computer
Client computer is one that is connected to the Network server to receive services from the
server.
Advantages of Client-server network
It offers a reliable centralized storage and sharing of files.
It ensures high security of the network through access controls installed on the server.
It is easy to monitor the network performance on the server
It is easy to solve network problems.
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It’s cheap to install software which can be done on the server alone instead of all
computers on the network.
Disadvantages of client-server network
It’s expensive to setup.
Extra expenses on buying a server computer
Extra expenses on hiring a network administrator
The server is one point of failure. In case the server fails to work, the whole network
comes to a standstill
NB:
The major difference between peer – peer and client – server network lies in how the
data and information is stored.
Metropolitan Area Networks (MAN)
A metropolitan Area network is a computer network that connects two or more local area
networks together which are geographically separated but in the same city.
Routers, switches and hubs are the hardware devices used to create metropolitan Area network.
Wide Area Networks (WANs)
A wide area network is a network that connects two or more local area networks together over a
large geographical distance such as across districts, cities or regions. WANs make use of a wider
variety of communication media compared to LANs including Telephone lines, Microwave links
(wireless), Satellite connections and fiber optic cables.
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Wireless local area network (WLAN)
Wireless local area network is a type of network that connects computers and other devices
provides in a small geographical using wireless distribution methods such as radio signals,
infrared or microwave or Bluetooth to communicate between the workstations and other devices.
Examples of wireless local area network devices are;
Wireless adaptor/card
Wireless Access Point
Wireless Bridge
Wireless router
Antennae
Wireless adaptor/card is a device that provides an interface between the network
operating system and an antenna to create a wireless connection to the network.
Wireless Access Point (WAP) is a device that connects wireless communication devices
together to form a wireless network. For a computer to be able to communicate with
wireless device, it must have a wireless network adaptor.
N.B Access Point (AP) is a wireless equivalent of a hub that receives buffers, and transmits data
by means of a wireless antenna between wireless local area network and a wired network
Wireless Bridge (outdoor local area network bridge) is a device used to connect local
area networks in different buildings.
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Antenna is a structure made of metal rods or wires which receives and sends out radio
and television signals.
Wireless Local Area Network (WLAN) topologies
Wireless Local Area Network can be built with one of the following topologies:
Peer- to – Peer (Ad hoc) topology
Access Point – based topology
Point –to– Multipoint bridge topology
Peer –to- Peer (ad hoc) topology
This is a type of topology where devices are configured to communicate directly to each other.
Access point – based topology
This is a type of topology where access point(s) are used to enable a wireless device to
communicate with any other wired or wireless device on the network.
Access points are used to bridge traffic onto a wired or wireless backbone, or where network
devices are interconnected using access points.
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Access points
Point – to – multipoint bridge topology
This is a wireless local area network topology where a wireless bridge is configured to connect a
LAN in one building to a LAN in another building even if the buildings are not close together but
within a clear line of sight.
Wireless Wide area network (WWAN)
This is a wireless network over a wide area in which separate areas of coverage are connected
wirelessly.
Examples of Wireless Wide Area Networks equipments especially long distance wireless
Satellite
Microwave dishes
Microwave antennae
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Wireless application Protocol (WAP)
The Wireless Application Protocol (WAP) refers to a group of related technologies and protocols
widely used as a standard protocol in providing Internet access to mobile phones or other small
mobile devices.
International network (Internet)
Internet is an International/global interconnection of computer networks. It is described as a
network of networks; it is a global network where all LANs (both big and small) worldwide are
interlinked. These networks connect together in many different ways to form the single entity
that we know as the Internet. In fact, the very name comes from this idea of interconnected
networks.
Network topology
Topology is the physical and logical arrangement of a local area network. The physical topology
of a network refers to the physical arrangement of cables, computers, and other peripheral
devices in relation to each other on a network meanwhile Logical topology is the method used to
pass information between workstations on a network.
Types of physical network topologies
Bus network topology
Ring network topology
Star network topology
Hierarchical network topology
Mesh network topology
Hybrid topology
Tree topology
Point-to-Point
Bus topology or linear bus topology
Bus network topology is one that consists of a main, central cable known as the backbone with a
terminator at each end of it where all devices on the network are connected to the main/central
cable.
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Advantages of Bus topology
It is less expensive than a star topology due to less footage of cabling, only needs one main
cable and no network hubs
It is good for smaller networks not requiring higher speeds
It has a high transmission speed if coaxial cable is used.
It is easy to add new workstations on the net work.
Multiple servers can be used.
Easy to connect a computer or peripheral to a bus.
Requires less cable length than a star topology.
Failure of one device doesn‘t affect others.
Disadvantages of Bus network
It is Limited in size and speed
The Entire network shuts down if there is a break in the main cable.
Difficult to troubleshoot. it is difficult to identify the problem if the entire network shuts
down
It is less secure since all data is transmitted down one main cable.
Transmission slows down as more work stations are added.
If the main cable fails, then all workstations are affected.
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Ring topology
This is a topology where all devices on the network are connected to one another in the shape of a
closed ring or a loop to form a ring. Data travels in form of a packet from one device to another
device around the entire ring in only one direction until it reaches its final destination.
In a ring topology, there are nodes and the work of these nodes is examined any data that
passes by to see if it is the address; if not, the data is passed on to the next node in the
ring.
Advantages of ring topology
It is a Very orderly network where every device has access to the token and the
opportunity to transmit
It performs better than a star topology under heavy network load
Can create much larger network using Token Ring
It is Cheaper to install than star network as there is only one cable between each
workstation.
High speed can be achieved as each workstation can boast the signal.
Disadvantages of a Ring network
One malfunctioning workstation or bad port in the central hub can create problems for the
entire network
Moves, additions and changes of devices affect the entire network.
Network adapter cards are expensive.
It is much slower than an Ethernet network under normal load
Less secure than star network as data pass through a number of workstations before
reaching its destination.
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Star topology
A star topology is a type of topology designed where computers and other devices are connected
directly to a central network hub or switch thus forming star.
Data on a star network passes through the hub or switch before continuing to its destination. The
hub or switch manages and controls all functions of the network.
Extended Star topology
This is a network where more than one individual’s star topologies are connected together. At the
center of the star is a hub or a switch. It extends the length and size of the network.
Advantages of Star /extended star topologies
It is suited for large networks
It is easy to expand the network without any negative effects
If one cable or station fails, the entire network is not affected
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It is easy to install, maintain and troubleshoot because the problem usually isolates itself.
Different types of cables can be used to maximize efficiency.
High speed transmission is possible since each station has a dedicated cable.
Greater security as connection from one station to server is unique.
No disruptions to the network when connecting or removing devices.
Disadvantages of Star/extended star topologies
Breakdown of the switch/Hub becomes a single point of network failure
It’s expensive to set up due to increased cabling costs and the need for a switch or hub.
Mass of cables are needed around in case of a large network.
If the cable fails the workstation cannot receive data via any other route.
The server can get congested as all communication must pass through it
Requires more cable length than a bus topology.
If the hub or switch fails, nodes attached are disabled.
Hierarchical topology
This is a type of topology that resembles extended star topology, except that computer controls
traffic instead of a hub or a switch.
Hybrid Topology
Hybrid topology is combination of two or more different topologies (bus, star, ring, etc.). The
hybrid network is based on both peer-to-peer and client-server relationship.
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A hybrid topology is easier to connect to other computers than some other topologies. Also the
hybrid topology has a faster connection.
Advantages of hybrid topology
Very reliable and easy to detect the faulty system.
It is easy to troubleshoot.
It includes both wired and wireless network.
It is expandable network.
Disadvantages of hybrid topology
Its design is difficult to understand.
The cost of this network design is high, because of requirement of lot of cables, cooling
systems, etc.
MAU (Multi-station Access Unit) is required.
It is expensive to install and maintain
Tree topology
A tree topology is a type of network topology that has combined characteristics of bus and star
topologies; it consists of groups of star-configured workstations connected to a bus backbone
cable.
Tree topologies allow for the expansion of an existing network, and enable organizations to
configure a network to meet their needs. It can be used to connect a bus network in buildings onto
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star topologies in different buildings.
Advantages of Tree topology
Allows for Point-to-point wiring for individual segments.
Expansion of Network is possible and easy.
It is easy to manage and maintain because the network is divided into segment
Error detection and correction is easy.
If one segment is damaged, other segments are not affected
Disadvantages Tree topology
Overall length of each segment is limited by the type of cabling used.
If the backbone line breaks, the entire segment goes down.
More difficult to configure and wire than other topologies.
Difficult to troubleshoot problem.
This network is not secure, anyone can see transmitted data.
As more and more nodes and segments are added, the maintenance becomes difficult.
Mesh topology
This is a network where each device has its own connections to all other devices on the network.
It provides each device with a point-to-point connection to every other device in the network.
Data sent on a mesh network can take any of the several paths from the source to the destination.
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Advantages of Mesh topology
A mesh topology provides much protection from interruption of service because of
possible routes through the network that is the damage of one or several cables or
computers may not have vital impact except the involved computers
Mesh networks provide redundancy, in the event of a link failure; meshed networks
enable data to be routed through any other site connected to the network.
Disadvantages Mesh topology
Much cabling is needed hence expensive
Not easy to troubleshoot incase of failure
Not easy to install.
It is the most expensive and difficult to maintain topology because each device has a
point-to-point connection to every other device.
The damage of at least one cable or device may damage the network seriously If there are
only few cables in the network
Point-to-Point Topology
Point-to-point (PTP) topology is a type of topology that connects two nodes directly together.
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The following examples are pure point to point links:
Two computers communicating via modems.
A mainframe terminal communicating with a front end processor.
A workstation communicating along a parallel cable to a printer.
Summary of physical types of topologies
Logical topology (Media Access Method)
Logical topology is how computing devices access the network and send data over the network.
The logical topology of a network determines how the devices communicate across the medium.
There are four commonly used media access methods:
A. Ethernet,
B. Token Ring,
C. Local Talk, and
D. Fiber Distributed Data Interface (FDDI)
E. Packet switching
F. Circuit switching
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Ethernet
Ethernet is a type of local area network technology that uses coaxial cable or special grades of
twisted pair wires. Ethernet is also used in wireless LANs.
Token Ring
A network topology developed by IBM in which computers access the network through token-
passing.
A Token is a special packet that contains data and acts as a messenger/carrier between each
computer and device on a ring topology.
Each computer must wait for the token to stop at its node before it can send data over the
network so as to avoid collision of data packets on the network.
Token passing
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Local Talk
Local Talk is a network access method designed by Apple Computer, Inc. specifically for
networking Macintosh computers • It provided a simple, cost-effective way of interconnecting
Macintosh devices • Local Talk uses a transmission method called Carrier Sense Multiple Access
with Collision Avoidance (CSMA/CA) • Local Talk relies on the AppleTalk protocol, but it may
also support the Macintosh version of TCP/IP called Mac TCP.
FDDI (Fiber Distributed Data Interface)
FDDI is a network topology that is used primarily to interconnect two or more local area
networks, often over large distances.
It uses fiber optics for speeds of up to 100 Mbps. It is used primarily to interconnect two or more
LANs, often over long distances
It also employs Token Ring passing process to transmit data; but use a dual counter-rotating ring
topology, meaning there are two rings of cable with two tokens circulating in opposite directions.
Packet switching
This is a data transmission technique which involves transmitting and routing of messages by
dividing the electronic message/data into packet segments and sending them rapidly and
sequentially over a network channel which are then reassembled into the original message at
their destination.
It involves breaking the data into individual segments known as packets which are transmitted
individually and then re-assembled when they reach the destination computer.
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Circuit switching
Circuit switching is a method of communicating in which a dedicated communications path
referred to as a circuit or channel is established between two devices through one or more
intermediate switching nodes before communication between the devices takes place.
Each circuit that is dedicated cannot be used by others on the network until the circuit is released
and a new connection is set up. The telephone system uses circuit switching.
Summary Chart:
Physical Topology Common Cable Common Protocol
Linear Bus Twisted pair, Coaxial & fiber Ethernet & Local Talk
Star Twisted pair & Fiber Ethernet & Local Talk
Star-Wired Ring Twisted pair Token Ring
Tree Twisted pair, Coaxial &fiber Ethernet
Factors to consider when choosing a network topology
Cost of installation. A linear bus network may be the least expensive way to install a
network; you do not have to purchase concentrators.
Number of computers and other devices to connect/size of the organization
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The architecture of the building to be used
The purpose of the network
Distance of connectivity
Safety provisions of the network
Personnel provisions/technicalities involved
Ease in accessing the network
Length of cable needed. The linear bus network uses shorter lengths of cable.
Future growth for instance with a star topology, expanding a network is easily done by
adding another concentrator
Cable type to use that is the most common cable in schools is unshielded twisted pair,
which is most often used with star topologies.
Network and Data security
Network and data security consists of the provisions made on computer network and policies
adopted by the network administrator to protect the network and the network-accessible
resources from unauthorized access to data, as well as guarding against Data loss and the
effectiveness (or lack) of these measures combined together.
Common computer Network problems and troubleshooting
Internet protocol (IP) conflicts that is when two computers are assigned the same IP
address erroneously
Solution: change the IP address for one of the computers.
Absence of connectivity
Solution: checking the physical connections and connection devices. And the distance between
devices in case of wireless network.
Check the router or hub to see if some machine is disconnected, or if it a case of is a faulty cable.
In this case: a good connection is shown by a green light.
Ensure that TCP/IP is configured.
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Ensure all the computers on the network are within the same subnet with individual IP addresses.
Check if the file and printer sharing option is installed and functioning, and also define network
shares on each computer.
Slow connectivity: This can be due to i) collisions, which the network is incapable of
handling. ii) Heavy file transfers bring down the speed tremendously. iii) the network
card may also be overloaded.
The Solution: i) zip bulky files while transferring, which lower the pressure on the network.
ii) Check if the network card is not suspended in the transmit mode, which indicates that the
card is working overtime. All you need to do in such cases is, to replace the faulty components.
Firewall settings can interfere with file sharing on connected computers. It is true
that disabling security features can make your system vulnerable to attacks, but lowering
security levels should not cause too much trouble.
The Solution: Rigid Firewall settings need to be adjusted to allow networked computers to share
data. You may consider disabling the security settings temporarily, after having thoroughly
considered all security related threats.
Factors that affect the rate of transmission on a network
Several factors that can negatively affect latency include the distance between the two points, the
type of transmission media, and the number of nodes through which the data must travel over the
communications channel. For best performance, bandwidth should be high and latency low;
Frequency and bandwidth of the medium;[rate of transmission]. The higher the frequency, the
wider the bandwidth, the more data will be sent over a medium and vice versa.
NB; Bandwidth; is the difference between the highest frequency and the lowest frequency.
Line configurations; these are either point – to – point or Multipoint. A point – to – point
connects the sending and receiving devices such that a terminal with a central computer.
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A Multipoint line is a single line that interconnects several communications devices to one
computer. Data moves faster in a point – to point than in a multipoint.
Serial and parallel transmission
In serial transmission, bits are transmitted sequentially, one after the other. In parallel
transmission, bits are transmitted through separate lines simultaneously. Therefore, data
transmission is faster in parallel transmission than in serial.
Direction of transmission
This can be simplex, half duplex or full duplex. In simplex, data can travel only in one direction.
In half duplex, data travels in both directions but only one direction at a time. In full duplex, data
travels back and forth at the same time.
Transmission mode
This can be either asynchronous or synchronous. In asynchronous transmission, data is sent one
byte (character) at a time. In synchronous transmission, large quantities of data are transmitted at
ago at regular intervals.
Packet switching
A packet is a block of data for transmission over a network. Packet switching is a technique for
dividing electronic messages into packets for transmission over a network to their destination
through the most convenient route. It can handle high volume of traffic in a network; It allows
more users to share a network, thereby offering cost savings.
Protocols (rules for data transmission)
A protocol specifies the type of electrical connections used the timing of message exchange,
error detection techniques; specify how the receiving devices will acknowledge sending devices
(handshaking) etc.
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Network topology
There may be data collisions in a bus topology hence slowing down the network. A star and ring
topology has fewer collisions and usually runs faster.
Capacity of hardware in the network
The speeds of hubs, switches and NICs will greatly determine the speed of the network.
The server
The amount of RAM installed in the server and the speed of the hard disk greatly affects the
speed of the network.
Location of software and files
If software is stored on the workstation hard disks, it increases (speeds up) performance and
reduces network traffic.
Qn .Differentiate between standalone computers and networked computers
A standalone computers are computers that are not connected to a network and is capable of
performing the operations in the information processing cycle meanwhile Networked computers
are computers designed specifically to connect to a network especially the internet.
TOPIC 11: INTERNET AND WORLD WIDE WEB
Definition of internet
Internet is an International/global interconnection of computer networks It is described as a
network of networks; it is a global network where all LANs (both big and small) worldwide are
interlinked.
These networks connect together in many different ways to form the single entity that we know as
the Internet. In fact, the very name comes from this idea of interconnected networks.
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History of the Internet
The Internet was originally developed in the late 1960’s by the US government department of
defense to improve secure communication between its military computers and enhance the
sharing of information and collaboration on military and scientific projects in four locations;
universities of California, Los Angeles, Santa Barbara, Utah and Stanford research institute.
This internet was known as ARPANET (Advanced Research Projects agency Network).
Characteristics of internet
It is made up of numerous networks worldwide.
There is No organization that has a direct control over the Internet.
It is dynamic; ever changing.
It offers very many services
The Internet size and technology is growing at a very faster rate.
It is not owned by any single organization (has no central control.
Advantages of using internet
The biggest benefit offer by internet is that it is a source of all valuable information
The primary goal of internet is communication because it offers a speedy communication
through the use of e-mail
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The internet is now the most popular form of entertainment. Movies, songs, videos,
games etc. is available and can easily be downloaded from the internet
Internet has facilitated social networking that is the sharing of information to people
across the world. Any job vacancy, emergency news, ideas etc. can be shared in the
social networking websites such as Face book, what saps, twitter etc
As far as learning is concern, internet has now become a part of education in the sense
that online studies, e-library, uploading educational information’s, and research can
easily be carried out using internet.
All business deals can be carried in the internet like transaction of money that is e-money,
online reservations, online ticket booking for movie, online shopping, advertising for
goods and services.
Disadvantages of using internet
Internet leads to the loss of information that is information crucial to us or any important
files can be easily taken by the hackers.
Internet offers high possibility for the fraudulent people to easily access personal details
such as names, address, credit card number etc
Networked computers connected to internet are susceptible to virus attack leading the
crushing of the hard disk and alternate the normal behaviors of the computer.
Internet allows any body to access and down unnecessary materials and pornographic
photos and films hence leading to moral degeneration in the society
Internet had led to social disconnecting in the society that is reduction into face to face
interaction for example the use of social media such as face book, what sap, twitter etc.
Internet has also led to the distribution of unwanted bulky e-mails (spamming)
Uses of internet as a learning tool
Used to search for information using search engines and directories
E-mail system is used in collaborative learning.
Enables distance learning for those who are unable to attend collage/school physically.
Allow discussions over educational chat rooms.
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Enables downloading of relevant documents.
Using computer assisted assessments (CAA) for online exams.
It enables the use of electronic libraries and textbooks.
Development of skills of research and communication by the students.
Assignment are received, done and sent across the network by the students.
Video conferencing is used to share views and ideas among students and teachers.
Advantages of internet in schools
A lot of information is obtained which is not available in a single textbook.
Updated or current information is obtained since internet is dynamic.
Learning is fun and easy as internet is exciting due to the multimedia content used.
It offers different sources of information hence a variety of opinions on a topic.
It is a quick way of getting information where internet connection is good.
It encourages group work through collaboration therefore sharing of information and
experience among students and teachers.
Related topics are easily accessible through hyperlinks.
Students are able to attend virtual classes.
Different skills such as typing, use of web browsers, problem solving, E-mail are
developed through the use of the Internet.
Instant or timely communication is done by use of the E-mail system.
Shopping for item such as books is made easy and less expensive.
Disadvantages of the Internet in schools
No Information control over the Internet such that all sorts of bad information is
accessed.
There is no privacy of information and information piracy is common.
Indecent materials are published on the Internet.
It’s not readily available to most people.
It is expensive to access drains school resources.
Time is lost where Internet speed is low due to poor links, hardware and congestion.
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Some sites give outdated therefore misleading information because they are not regularly
updated.
Time wasting occurs when students easily stray into non essential materials.
Many Internet sites have been commercialized therefore emphasize adverts and selling
such that less free academic content is given.
Computer viruses can easily spread over the Internet.
Difficult to obtain information relevant to a particular level of a student.
It is possible to obtain contradictory information.
Many students and teachers do not have adequate skills of accessing the Internet.
Possible solutions to Internet issues
Use of firewalls against illegal access to networks
Use of updated antivirus software against viruses
Use of anti spyware against hackers.
Carefully choosing an ISP who will provide the best service within your means.
Installing filters against pornographic and other undesirable content.
Use of encryption software to protect sensitive information and prevent fraud.
Use of complicated passwords to restrict access to.
Use of digital certificates. This is a means of authenticating that an organization is genuine
and that any transaction undertaken with it will be honored. The certificate contains the name
of the organization and a serial number registered with a Certification authority who issues
the certificate.
Internet protocols
The Internet Protocol (IP) is the method or a standard set of rules for sending and receiving data
from one computer to another on the internet. For a computer known as Host to be recognized by
other devices, it must have an internet protocol address.
Internet protocol (IP) address is a number that uniquely identifies each compute on the internet.
IP address consists of four groups of number, each separated by periods e.g. 192.168.5.6. The
first three values that 192.168.5 usually identifies the network and the last value that 6 represent
the specific computer
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Examples of internet protocols
Transmission communication protocol/internet protocol (TCP/IP)
Hypertext transfer protocol (HTTP)
File transfer protocol (FTP)
Basic requirements for internet connection
Host computer
Communication hardware such as Modem and router.
Communication Software such as a Web browser and internet protocols
Communication media such as VSAT, wireless antenna or telephone line.
Internet Service provider(ISP)
Internet service providers
Internet service provider (ISP) is a company that provides connection and services for accessing
and using the Internet at a monthly subscription fee.
Examples of internet service providers in Uganda
Airtel Uganda limited
Mtn Uganda limited
Africel Uganda limited
Uganda telecom limited (UTL)
Roke Uganda limited
Infocom Uganda limited etc
Services offered by internet service providers
They offer internet access and internet connectivity
They do system analysis and consultancy
They provide network servicing and maintenance
They Provide network security
They provide other services like website hosting
They facilitate domain name registration
They provide electronic mail services
They facilitate video conferencing
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Factors to consider when choosing an internet service provider (ISP)
Setup costs
Experience for both ISP and client.
Auxiliary/additional services offered by the ISP e.g. E – Mail/telephone SMS facility.
Availability of online help.
Compatibility of ISP software with yours e.g. windows Vs Linux Vs Wang.
Efficiency/Effectiveness of ISP devices e.g. speeds of ISP modem, Bandwidth etc. cabling
architecture, Bit–Bus architecture for devices etc.
Available technology. For example, In case you intend to hire a dial-up service, you need to
consider the availability of a local phone number or toll-free number for access; this would
help to reduce cost of acquiring totally new technology or equipment.
You also need to consider the Technology offered by the ISP. Some technologies are older
and less efficient than others. The ISP should be able to offer the latest and most efficient
technology.
Technical support. What kinds of support services can the ISP provide; Are there any
additional charges for support?
The terms of service. You need to consider the terms of services offered by the ISP and
determine whether they meet your expectations or not, for example, is there a limit to the
number of hours per month you can use the service or is there a limit to the amount of
download or upload per month?, does this fit well within your needs?
Other services offered by the ISP that you can have on top of internet connection. E.g. web
hosting and domain services.
The fee charged for the services. What is the monthly fee for the service? Are there any
additional equipment or setup fees? What is the fee for extra e-mail accounts web site
hosting, and how do the costs compare with other service provider companies?
The size of the ISP’s Client base. ISP capacity is usually limited, the bigger the client base
the less reliable is the ISP.
Coverage. Does the ISP coverage reach your location or not?
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Your Internet service needs. Suppose all you need to do is check e-mail and read web pages,
a dial-up connection may be enough. But most people also want to download music,
television shows, or watch videos. For these, you will need a faster connection with
broadband access, such as a digital subscriber line (DSL), a cable modem, or satellite.
Common terminologies used in internet connection
Dial-up (dun)
Bandwidth
Broadband internet access
Cable modem
Leased line
Bit rate
Dial-up (DUN)
This is a connection method where the client must request for a connection to the ISP server each
time he wishes to access the Internet.
Leased line
This is where there is a permanent connection between the user and the ISP at a fixed fee. This
connection normally uses digital subscriber line (DSL) technology
Cable modem
A cable modem is a type of modem that provides access to a data signal sent over the cable
television infrastructure. Cable modems are primarily used to deliver broadband Internet access,
taking advantage of unused bandwidth on a cable television network.
Broadband Internet access
Broadband Internet access (broadband) is high-speed Internet access.
Bandwidth
Bandwidth is the amount of Data that can be transmitted along a communication channel in a
given period of time which is measured in bits per second. The larger the range of frequencies, the
greater the amount of data that can be transmitted
Bit rate
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Bit rate is the speed at which a particular transmission is taking place. It is measured in bits per
second (bit/s or bps) and represents the actual speed of transfer of data.
Factors that determines the internet access speed
The amount of bandwidth allocated by ISP.
Connection technology used; telephone lines are much slower than newer technology such
as ISDN and ADSL.
The volume of traffic. The more the number of people logged on the internet the slower
the internet speed.
Adapter or modem speed used.
The processing speed and amount of RAM of the host computer
Type of data/files being downloaded or uploaded.
The age of computer set, whether clone or new
Services offered by internet communication
Chat rooms
Mailing lists
Instant messaging (IM)
Internet Relay chat (IRC)
News group
Message board (Internet forum)
Voice over internet protocol (VoIP)
Usenet
Video conferencing
Telnet
Electronic commerce (e-commerce)
Social network
Internet banking (e-banking)
Search Engine (Web Search)
Wikis and blogs
Discussion boards
Portals.
Podcasts.
E- Libraries
Electronic waste (e-waste)
World wide web (www)
Chat rooms
A chat room is an online service that permits users to chat (converse) with each other
through the internet, traditionally in plain text only by typing lines of text in the
computer.
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To start a chat session, a user must connect to a chat server through a chat program on his or her
computer. Some chat rooms support voice chats and video chats.
More recent developments in Web technology now allow the transmission of images
and emoticons in a chat room as well. Some chat rooms require a username and
password combination in order to log in or join a conversation, allowing for privacy
among the users.
Mailing lists
A mailing list also known as an email list or electronic mailing list is a collection of names and
addresses used by an individual or an organization to send material to multiple recipients. Rather
than individually sending an email to each user, mailing lists send email to specific user groups
through a single email message. The term is often extended to include the people subscribed to
such a list, so the group of subscribers is referred to as "the mailing list", or simply "the list".
Mailing lists are generally used as a means to share content, news and any
product- or service-related information with subscribers that is when a message is
sent to a mailing list, every person in the list will receive a copy of the message.
Instant messaging (IM)
Instant messaging (IM) technology is a type of online chat that offers real-time text
transmission over the Internet between two parties, when each user chooses to
complete a thought and select "send".
Internet Relay chat (IRC)
Internet Relay Chat (IRC) is a text based communication
system that allow people to chat with one another on the Internet within the chart room. It allows
people within the same chart room to send and receive instant message
News group
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A newsgroup also called a discussion group is an online discussion forum accessible
through Usenet about a particular subject. To participate in a discussion, a user sends a
message to the news group and other users in the news group read and reply to the
message.
Internet forum (Message board)
An Internet forum, or message board, is an online discussion site where people can hold
conversations in the form of posted messages. They differ from chat rooms in that messages are
often longer than one line of text, and are at least temporarily archived.
Voice over internet protocol (VoIP)
Voice over Internet Protocol (also voice over IP, VoIP or IP telephony) is a methodology and
group of technologies for the delivery of voice communications and multimedia sessions
over Internet Protocol (IP) networks, such as the Internet.
Usenet
Usenet is a collection of newsgroup where the users can post messages and these posted
messages are distributed via Usenet servers. Each server holds the posted messages for a certain
period of time which is also known as retention time. Usenet can be compared with an internet
forum, but the main difference is that the messages are not stored in one server and are only
available for a certain amount of time.
Video conferencing
Video conferencing (or video conference) is a mean of conducting a
session/conference/discussion using a set of telecommunication technologies between two or
more participants at different geographical locations by using computer networks to transmit
audio and video data. Each participant has a video camera, microphone, and speakers mounted
on his or her computer. As the two participants speak to one another, their voices are carried over
the network and delivered to the other's speakers, and whatever images appear in front of the
video camera appear in a window on the other participant's monitor.
Telnet
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Telnet is a protocol used on the Internet or local area networks to provide a bidirectional
interactive text-oriented communication facility using a virtual terminal connection.
Electronic commerce (e-commerce)
E-commerce (electronic commerce or EC) is the buying and selling of goods and services, or
the transmitting of funds or data, over an electronic network, primarily the internet. These
business transactions occur either as business-to-business, business-to-consumer, consumer-to-
consumer or consumer-to-business
Business – to - Consumer (B2C)
This is a business transaction model that applies to any business that sells its
products or services to consumers over the internet.
Consumer – to Consumer (C2C)
This is a model that applies to sites primarily offering goods and services that
assist consumers interacting with each other over the Internet.
Business – to – Business (B2B)
Is the e – commerce which consists of businesses buying from and selling to each other
over the internet.
Consumer – to – Business (C2B)
This transaction applies to any consumer that sells a product or service to a business
over the internet.
Examples of transactions conducted online
Online shopping
Online banking
Advantages of e – commerce
It operates 24 hours a day hence transactions can be conducted at anytime.
Information about a product can be changed and be available quickly (i.e. it is easy to
update)
It gives immediate feedback
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Allows manufacturers to buy and sell their products directly hence avoiding the cost of
middlemen.
Customers can easily compare prices.
It allows business to gather customer’s information, analyze it and react appropriately.
Businesses have access to millions of people with internet connections.
It widens the market easily. It can work globally hence saving time for participants on
both ends.
Distribution costs for information is reduced or completely eliminated.
It allows business companies to advertise for their products easily.
Social network
This is a dedicated website which enables users to post comments, and communicate with each
other to share their interests, ideas, stories, photos, music, and videos with other registered users
via internet by using social media such as face book, Twitter, MySpace, Bebo. Instagram, what
sap etc.
Bebo is a popular social networking site where users can share photos, stories, their journal, and
more with friends and family privately or publicly on the Internet.
Classmates is one of the largest and most used websites for connecting people who graduated
from a high school and allows you to keep in touch with them and any future reunions.
Face book is a popular destination for users to set up personal space and connect with friends,
share pictures, share movies, talk about what you're doing, etc.
Instagram is a mobile photo sharing service and application available for the iPhone, Android,
and Windows Phone platforms.
LinkedIn is one of the best if not the best locations to connect with current and past co-workers
and potentially future employers.
Twitter is another fantastic service that allows users to post 140 character long posts from their
phones and on the Internet.
Internet banking (e-banking)
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Internet banking also known as electronic baking or online banking is an electronic payment
system that enables customers of a bank or other financial institutes to conduct a range
of financial transactions through the financial institution's website.
It is a method designed to enable the customers to have easy and safe access to the bank account
in order to carry out online transaction services electronically via the Internet.
Internet banking enables the following:
Accurate statement of all means available in your bank account
Statement of current account, credits, overdrafts and your deposits
Execution of national and international transfers in various currencies
Execution of all types of utility bill payments (electricity, water supply, telephone bills,
etc...)
Carrying out customs payments
Electronic confirmation for all transactions executed by E-banking
Management of your credit cards
Search Engine (Web Search).
Search engine is a service that allows Internet users to search for content via the World Wide
Web (WWW). A user enters keywords or key phrases into a search engine and receives a list of
Web content results in the form of websites, images, videos or other online data.
It is a software program or script available through the Internet that searches documents and files
for keywords and returns the results of any files containing those keywords. Today, there are
thousands of different search engines available on the Internet, each with their own abilities and
features and the most popular and well-known search engine is Google. Other popular search
engines include AOL, Ask.com, Baidu, Bing and Yahoo.
Wikis and blogs
A wiki is a website that allows multiple users to create, modify and organize web page content in
a collaborative manner via their web browsers. Wiki documents can be modified by anyone with
access to the website. It's a shared-authorship model; users can add new content and revise
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existing content without asking for permission to do so. One of the largest and best-known
examples of a wiki is the Wikipedia free online encyclopedia.
A blog is a website where users post journal-like entries that are displayed in reverse
chronological order, with the most recent posting at the top of the page. Blogs can take the form
of online diaries, personal chronicles, travel logs, newsy columns and reports from special
events. They can include graphics, pictures, and even music and video clips.
Discussion boards
A discussion board is known by various other names such as discussion group, discussion forum,
message board, and online forum). It is a general term for any online "bulletin board" which
allows members to hold discussion online about a particular topic. Discussion is started by one
member posting a topic and other members of the same group begin to reply by sharing
information and ideas.
Portals.
A Web portal is a specially designed website that brings information from diverse sources, like
emails, online forums and search engines, together in a uniform way. Usually, each information
source gets its dedicated area on the page for displaying information (a port let); often, the user
can configure which ones to display. The extent to which content is displayed in a "uniform way"
may depend on the intended user and the intended purpose, as well as the diversity of the
content. Examples of portals include; HotBot, Alta Vista, Go.com, iGoogle, Excite, Yahoo etc.
Podcasts.
A podcast, or generically net cast, is an episodic series of digital audio or video files which a user
can download and listen to. It is often available for subscription, so that new episodes are
automatically downloaded via web syndication to the user's own local computer, mobile
application, or portable media player. It is distinct from Internet radio, which involves streaming
rather than downloading.
E- Libraries
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E-Library /Digital Library is a set of documents available through electronic means by the use of
digital technologies that allow for the retrieval, archiving, preservation, and dissemination of
those documents .It is a special library with a collection of digital objects that can include text,
visual material, audio material, video material, stored as electronic media formats as opposed to
print, or other media.
Electronic waste (e-waste)
Electronic waste is a term abbreviated as "E-Waste” which refers to the disposal of broken or
obsolete electrical and electronic equipments (EEE) and its parts that have been discarded by the
owner as waste without the intention of re-use them.
Netiquette
Netiquette is a short form of network etiquette or Internet etiquette. Netiquette is a combination
of the words network and etiquette, and is defined as a set of rules for acceptable online
behaviors. Similarly, online ethics focuses on the acceptable use of online resources in an online
social environment.
In general, netiquette is the set of professional and social etiquettes practiced and advocated in
electronic communication over any computer network. Common guidelines include being
courteous and precise, and avoiding cyber-bullying. Netiquette also dictates that users should
obey copyright laws and avoid overusing emoticons.
Rules of netiquette
Keep messages brief by using proper grammar, spelling and punctuation.
Be careful when using sarcasm and humor as it might be misinterpreted.
Be polite and void offensive languages.
Read the message before you send it.
Use meaningful subject lines
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Avoid sending or posting flames, which are abusive or insulting messages.
Avoid sending spam, which is the internet‘s version of junk mail.
Do not use all capital letters which is equivalent to SHOUTING!
Read the FAQ (Frequently Asked Questions), if one exists. Many news groups and
web pages have a FAQ.
Do not assume material is accurate or up-to-date. Be forgiving of other’s mistakes.
Never read someone’s-mails.
Differentiate between internet, intranet and extranet
Electronic mail (e-mail)
Electronic Mail is a method of exchanging messages between people using electronic devices. In
order for any two users to receive or exchange E-mail messages online, they must have E- mail
addresses.
E – Mail address
E-mail address is a set of characters such as letters, number, symbols etc that are required to send
and receive emails
Parts of an email address
Email address consist of four parts;
Consider this email address: tobbyecat@gmail.com
1. Username: tobbyecat
2. @: at
3. Domain name: Gmail
4. Top level domain: com
Username:
A username is a name that uniquely identifies someone account on the email server that handles
the email.
@:
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It separates username or account name from the name of the mail server.
Domain name:
It consists of Email server name (Gmail, yahoo, hotmail) that comes after the @ symbol in
an email address
A top level domain:
A top level domain refers to the last segment of a domain name, or the part that follows
immediately after the "dot" symbol. It usually a three letter extension which shows the type of a
particular organization.
Examples of top level domain names
Top-level domain name Purpose of host.com a business or commercial enterprise (trying to make money).ac an academic institution or a university.edu host is an educational institution.org a non-commercial organization.mil Military.net for network(ISP).gov Government
Country-codes Country.ca Canada.au Australia.nz New Zealand.ug Uganda.uk United Kingdom.za South Africa
Sending and receiving of an email
To send and receive emails, both the sender and the recipient must have the right tools.
An internet connection
An email address
An email client
Email client is software that runs on a personal computer and relies on an internet
connection to perform some of its operations.
It works with ISP (Internet Service Provider) that uses standard internet email protocols
that make i possible for people using different email client software to communicate with
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one another.
Features of an email account
After successful signing in, the email service provider automatically provides your
account with features like:
Inbox for incoming massages
Outbox for outgoing massaged
Address box for storing your personal email address etc
Email message
An email message is a text, typically brief and informal, that is sent or received over a computer
network including attachments (such as image files and spreadsheets). Email message can be
sent to multiple recipients at the same time.
Email message comprises of the 3 parts, these are:-
1. Message Header
2. Message Body
3. Message Envelope
Message Headers
The message headers contain information concerning the sender and recipients. The exact
content of mail headers can vary depending on the email system that generated the message.
Generally, headers contain the following information:
From: Contains the E-mail address and the actual name of the sender of the e-
mail message.
To: Contains the E-mail address and the actual name of the recipient of the e-
mail message
Date: Contains the date and time when the E-mail message is sent.
Cc: Carbon Copy
Contains another E-mail address (es) of recipients to whom the same copy of the
E- mail message is being sent.
The recipients of such an E-mail are able to view the e-mail addresses of all
the other recipients who have received the same mail.
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Bcc: Blind Carbon Copy
Contains another E-mail address (es) of recipients to whom the same copy of the
E- mail message is being sent.
But the recipients of such an E-mail are not able to view the e-mail addresses of all
the other recipients who have received the same email.
Subject: Contains the main theme/topic/content of the mail message.
Text area: This is the main area where the user enters/ types text to be sent as the
main mail.
Attachment: This is the area that enables the user to link non textural documents e.g.
photos, music, videos etc. to the email message to be sent together.
Send: This is the tab that issues instructions to clients email software to post the
massage
Message Body
The email body is the main part of an email message. It contains the message's text, images and
other data (such as attachments)
The message body must include salutation, the actual message, complimentary close, and a
signature or automatically generated text that is inserted by the sender's email system.
Message Envelope
When email is handed over from the sending computer to the receiving computer, the sending
computer declares a sender address (the “envelope-from", which is the address that
bounce messages will go to if delivery fails at a later stage) and one or more recipient addresses
("envelope-to").
Notice: For one to create email address and access to e-mail via the Web, he or she is required to
enter a username and a password.
A username is a name that uniquely identifies someone account on the email server that handles
the email.
A password is a private combination of characters associated with the user name that
allows access to certain computer resources or to a network. The password helps to
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ensure that unauthorized users do not access the computer.
Characteristics of a good password
Should be easy to remember but not too obvious.
Should be longer, at least eight characters.
Should have a combination of mixed case letters and digits.
Should be easy to type without looking at the keyboard.
Avoid the followings with a password
Using your name, birthday, ID card number or telephone number.
A password of all digits or all the same letter.
Safeguarding your password
Do not share your password with others
Do not write down your password
Change your password frequently
Advantages of email
It is very quick to communicate quickly with anyone on the Internet.
It is a cheap means of transferring files.
Other computer files can be attached to the email.
Records and copies are kept automatically online.
Can be picked up anywhere in the world.
Can be sent at any time to its destination (it works24-7)
You can deal with your email at a convenient time.
You can send letters, notes, files, data, or reports all using the same techniques.
Disadvantages of an email
A computer and other hardware such as a modem are required hence expensive
It is not secure
It is easy to get on junk (useless) mail lists.
Email isn't necessarily private. Since messages are passed from one system to
another, and sometimes through several systems or networks, there are many
opportunities for someone to intercept or read email
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Some email systems can send or receive text files only.
It's possible to forge email. This is not common, but it is possible to forge the address
of the sender. You may want to take steps to confirm the source of some email you
receive.
It's difficult to express emotion using email. The recipient doesn't have the benefit of
seeing your facial expressions or hearing your voice.
In case of any error in the address, email cannot be delivered.
Email consumes a lot of time hence promoting laziness
Parcels cannot be delivered via email which limit its usability
World Wide Web (www)
The World Wide Web (abbreviated as WWW or the Web) is an information space where
documents and other web resources are identified by Uniform Resource Locators (URLs),
interlinked by hypertext links, and can be accessed via the Internet. It is where all the Web pages,
pictures, videos and other online contents can be accessed via a Web browser.
Common terms used in World Wide Web
Web page
Web server
Web master
Hyperlinks
Web publishing software
Domain name
Uniform Resource Locator (URL)
Web browser
Search engine
Website
A web page
A web page is an electronic document or files of information stored on the web /website that
contain text, animations, audio, and video (i.e. multimedia elements), as well as built – in
connections (called hyperlinks) to other documents.
A web server
A web server is a computer that keeps and delivers web pages requested by users.
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A webmaster
A web master is an individual person responsible for creating, managing and developing web
pages and maintaining a website.
Hyper links
These are built-in links to other related documents, allowing users to quickly navigate
from one document to another when clicked
Hyper text
Hyper text is a web page that has hyperlinks to other WebPages program used to access and view
web pages.
Homepage
Home page is the first page (starting page) or the table of contents of a website.
Web publishing software
Web publishing software is specially designed software designed for creating web pages
that contain text and multimedia elements. Examples include: Microsoft FrontPage,
Macromedia Dreamweaver, Adobe Go Live, Adobe Page mill etc.
Domain name
A domain name is the address which allows the Internet users to access a website. A domain
name is a website name. A domain name is used for finding and identifying computers on the
Internet. A domain name can be any combination of letters and numbers, and it can be used in
combination of the various domain name extensions, such as .com, .net and more.
No two websites can have the same domain name. A domain name is one that represents an IP
address of a computer on the network. It identifies the organization or group on the internet.
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An example; www.bbc.co.uk
The domain is separated into four parts just like the IP address. A user normally finds it easier to
use a domain name instead of an IP address to access the internet, but the internet protocol only
understands IP addresses so the domain name must be translated(resolved) into an IP address by
the DNS server (domain name system)
Name resolution
Name resolution is a technique that allows names to
represent network addresses.
For example, the website “yahoo.com" can be accessed without knowing the actual IP address
that the device at Yahoo is configured to use. A name resolution service translates, or "maps", the
name “yahoo.com" into an IP address to reach the destination device
Domain name system (DNS)
Domain Name System (DNS) is a system on a computer that maps text names to IP addresses
automatically.
The Domain Name System (DNS) translates the easily memorized domain names (e.g.
www.google.com) to the numerical IP addresses needed for the purpose of locating computer
services and devices worldwide. The Domain Name System is an essential component of the
functionality of the Internet.
For example www.bbc.co.uk
Www; indicates the host server
,bbc; is the name of the organization (second level domain).
.Co; refers to as the top or high level domain name which indicates the type of the organization.
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Domain name hierarchy on the domain name
The hierarchy of domains descends from the right to the left label in the domain. Each label
specifies a sub domain of the domain to the right.
Different levels of domain name;
Top level (highest level) domain name
Second level domain (SLD)
Third level domain
Top level (highest level) domain name
Top-level domain (TLD) is the last part of an Internet domain name, that is, the group of letters
that follow the final/last dot of a domain name.
Examples of top level domain
.org
.gov
.com
.net
Commonly used Top level domain names
.com indicates that the organization is a commercial one i.e. business
.gov indicates that it is for a government department
.ac is for an academic organization
.org is for a non commercial or non business organization
.sc is for a school organization
.net is for a company that provides internet services
Top level Domain of some countries
.uk which is the last part of the domain name indicates that the web site is based in the UK.
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Each country has been assigned a two letter code Such as;
.au for Australia
.de for German(Deutschland)
.it for Italy
.es for Spain (espania)
.ug for Uganda
Second level domain (SLD)
The second-level domain is the label directly to the left of the top level domain.
Third level domain
This is the part of the domain name that is immediately to the left of the second level domain
For example, given the domain name www.bbc.co.uk
.uk: The top level domain name
.co: Second level domain
.bbc: Third level domain
Www: The host server
Uniform resource locator (URL)
Uniform Resource Locator is defined as the global address of documents and other resources on
the World Wide Web.
Uniform Resource Locator is use to visit WebPages and other resources on the web. The URL is
an address that sends users to a specific resource online, such as a webpage, video or other
document or resource. When you search Google, for example, the search results will display the
URL of the resources that match your search query. The title in search results is simply a
hyperlink to the URL of the resource.
Example: http://www.yahoo.com/household/stampcollecting/welcome.html
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Parts of a Uniform resource locator (URL)
1. The protocol being used, which could be http or ftp
2. The domain name which is the location that contains the file of web page
3. The path to a web page which may contain a folder name and document file name both of
these separated by forward slashes
4. The query string, or parameters. These are optional but show information about the page/file
5. URLs don’t contain capital letters or spaces, but contains dots and forward slashes.
6. The Forward slashes specify the path to the location of the file needed.
Definition of a web browser (web Client)
This is the software program used to access and view web pages. A Web browser is
communication software designed to allow the user to access and view web pages (HTML
documents) on the Internet’s World Wide Web. The browser is designed to interpret hypertext
Markup (HTML) language.
HTML is a code in which web pages are written, therefore it requires a web browser which is
specialized software to able to retrieve and display text, and multi-media in HTML.
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A browser is a software application for retrieving, presenting and traversing information
resources on the World Wide Web.
Types of web browsers
Opera
Google Chrome
Mozilla Firefox
Microsoft Internet Explorer
Safari
Netscape
Sea Monkey
Camino
iCab
Mozilla Suite
Sunrise
Functions of a web browser
To request for web pages from a web server when the user type in the uniform resource
locator.
The web browser accesses information from the web server using the HTTP protocol
over a network to communicate with the web server.
It displays web pages on the screen.
It is used for steaming video content over the internet.
Displays multimedia content.
The followings can be done using web browsers
View hundreds of millions of WebPages.
Use mail clients to Send and receive e-mail.
Download games, music and computer software.
Chat
Shop on line
See and hear recorded broadcasts
Participate in virtual conferences
A view channel, a channel is a website that automatically transmits information to your
computer at the time you specify.
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Search engines
A search engine is software that allows one to search for web pages on the WWW by typing in a
search query relating to the topic that one is searching for.
It is a service that allows Internet users to search for content via the World Wide Web (WWW).
A user enters keywords or key phrases into a search engine and receives a list of Web content
results in the form of websites, images, videos or other online data.
It is a software program or script available through the Internet that searches documents and files
for keywords and returns the results of any files containing those keywords.
Different types of search engines
Features of a search engine
All pages are ranked by a computer algorithm not by subject category. They rank the most
relevant pages first or those that register most occurrences of the key word(s) usually more
accurate pages are listed before sites that include unreliable and erroneous material.
They are huge databases.
They are not evaluated-They contain the good and the bad so the user must evaluate
everything to determine its relevance.
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How search engines work
When the user type the key words in the search query in the search text box and presses ok button,
the search engine invokes a program that queries its database (a collection of all the web pages it
has access to). The results are returned to the user as a number of possible URL's ranked in
priority, the top URLs are the ones with most occurrences of the query words or phrases used.
Effective use of a search engine
Note that one can do a more complex search using more than one keyword and linking them
together with “AND” and “OR” or “NOT” (Boolean’s logic)
Be specific- e.g. if one wants to search about windows 98 bugs, the search query should be
“windows 98 bugs” not just “windows”
Using the symbols + or - the plus symbol lets you find pages that have all the words in the
query e.g. to get pages that refer to both john and Tom on the same page, use +john +Tom
Example 2 +computer +studies +schools gives pages on computer studies in schools
Use the – symbol to eliminate characters from the search.
Use parentheses to sequence operators and group words. Example; always group words
joined by OR with parentheses.
Narrow the search query to avoid irrelevant results.
Evaluation of search results
Not all that is published over the internet is good or accurate. So there is need to evaluate what
one finds. The following are the guidelines;
Accuracy
Is the information accurate?
Is it reliable and error-free?
Are the interpretations and implications reasonable?
Is there evidence to support conclusions?
Is the evidence verifiable?
Do the authors properly list their sources, references or citations with dates, page numbers
or web addresses, etc.?
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Objectivity
What is the purpose of information?
What do the authors want to accomplish?
Does this purpose affect the presentation?
Is the information fact, opinion, spoof, or satirical?
Currency
Is the information current (up to date)?
Is it still valid?
When the site was last updated?
Is the site well-maintained?
Are there any broken links?
Coverage
Is the information relevant to your topic and assignment?
What is the intended audience?
Is the material presented at an appropriate level?
Is the information complete?
A website
A web site is a collection of web pages where information of a particular organization or
company is stored.
Basic types of websites
News websites
Informational websites
Online Business / marketing
websites
Wikis
Online social networks
Educational websites
E- Commerce website
Mobile device websites
Blogs
Personal websites
Photo sharing websites
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News website
A news Web page contains news worthy material including stories, articles and videos relating
to current events, life, money, sports, weather etc.
Information website
Information website is a website that provides information such as census data, tax code, and
forms, government documents, public transportation schedules, and government budget and
research report.
E-commerce/ online business website
This is website that contains content that promotes selling and buying of goods, and services
online.
Educational website
An educational Web site offers exciting, challenging avenues for formal and information
teaching and learning. Some companies provide online training to employees and universities
offer online classes and degrees.
Entertainment website
An entertainment Web site offer music, videos, sports, games, ongoing Web episodes,
sweepstakes (Lottery), chats, and many other entertainment services.
Media sharing Web site
A media sharing Web site is a specific type of online social network that enables members to
share media such as photos, music, and videos.
Personal website
A personal Web page is maintained by a private individual who normally is not associated with
any organization. It is s type of website that allows an individual person to share with others
about his/her thoughts, photos, and experience including personal details.
Online Social Network website
An online social network also known as social networking Web site, is a Web site that
encourages members in its online community to share their interests, ideas, stories, photos,
music, and videos with other registered users. Examples include; Face book, twitter, what saps
etc.
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Advantages of social networking website
Disadvantages of social networking website
They are addictive.
They are not regarded as formal
In case one forgets his/her password, signing in is not possible and this can lead to loss
of information.
Social Networks may violate privacy in case someone else gets to know your user
password.
Misinterpretation: One has to be careful while posting any kind of information on social
networks. If typed in a hurry, the matter could be misinterpreted.
Junk Messages: Social Networks are used a lot to send unsolicited messages and
unwanted advertisements.
Why people visit a web site
i. To find information they need
ii. To buy something online
iii. To get various multimedia elements for entrainment
iv. To be part of the community through social media
v. To complete a task
Characteristics of a good web site
A web site must be supported by a reputable institution without bias in the information
A website should be written at an appropriate level
It should list the author and the appropriate credentials
It should be well organized and the links should work well
The information on the web page should be current
The pages at the web site should download quickly and be visually pleasing and easy to
navigate
It should contain little advertising and be free of preconceptions
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Functions of a web site
1. It acts as a source of information. It can be used in research to get information on the
internet about advertisements, entertainment, etc.
2. It helps users or a particular organization to share knowledge and information over the
internet
3. It provides motivations to the users of an organization
4. It encourages pride of ownership
5. It enhances communication and collaboration
6. It helps in storing important information for an organization.
7. It helps organizations in easy and quick advertisement of their products.
8. It enables organizations to upload and download information to and from the internet
respectively.
9. It helps organizations to easily maintain and update the information about them quickly
Importance of a web site to a school
1. It is used for communication purposes. The school can reach out to a wider audience
worldwide, for example, in school recruitment.
2. Used for mobilization of resources. The website can be used for resource mobilization as
it can reach out to a wide supporting audience.
3. For advertising purposes. The website can provide general information about the school.
4. The website can provide a forum for discussion of issues concerning the school using
blogs.
5. It can be used for teaching and learning in the following ways:
The website can provide subject content notes to students.
The website can present an opportunity for developing web designing technology
skills for students directly involved.
The school community can collaborate with other students worldwide for project
based learning.
6. The website can provide a forum for students and teachers to collaborate with others
elsewhere.
7. The site can provide a forum for parents and alumni feedback.
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8. It can work as a depository (store) where student’s achievement data is posted for easy
access by the stakeholders.
9. It can help teachers to collaborate with other teachers worldwide.
10. The site can be used to publish students and teachers work.
Limitations of a web site to a school
1. Websites are expensive to be constructed. Therefore, some institutions may not be in
position to come up with one.
2. They require a lot of maintenance and update hence becoming expensive and time
consuming.
3. They limit customers from directly interfacing with the business men. This makes
customers to sometimes be cheated.
4. Very many people and organizations are creating websites with a lot of information
which is not legitimate and some organizations lay the public through the websites.
Guidelines for evaluating the value of a Web site
The institution hosting a website should support the web site without bias in the
information
The web site should be written at an appropriate level
The web site should list the author and the appropriate credentials
The web site should be well organized and the links should work properly
The information on the web page should be current
The pages at the web site should download quickly and easy to navigate
The web site must be objective
TOPIC 12: ELEMENTARY COMPUTER PROGRAMMING
A program is a set of step-by-step instructions that directs the computer to do the tasks you want
it to do and produce the results you want.
A computer requires programs to function. A computer program is usually written by a computer
programmer in a programming language.
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A programming language is a set of rules that provides a way of telling a computer what
operations to perform.
A programmer, developer, dev, coder, or software engineer is a person who creates computer
software. The term computer programmer can refer to a specialist in one area of computers or to
a generalist who writes code for many kinds of software.
The roles of a programer
Converting problem solutions into instructions for the computer by preparing the
instructions of a computer program and runs those instructions on the computer, tests the
program to see if it is working properly, and makes corrections to the program.
The programmer also writes a report on the program. These activities are all done for the
purpose of helping a user fill a need, such as paying employees, billing customers, or
admitting students to college.
Computer programming is the process of writing instructions that get executed by computers.
The instructions, also known as code, are written in a programming language which
the computer can understand and use to perform a task or solve a problem.
There are at least three good reasons for learning programming:
Programming helps you understand computers. The computer is only a tool. If you learn
how to write simple programs, you will gain more knowledge about how a computer
works.
Writing a few simple programs increases your confidence level. Many people find great
personal satisfaction in creating a set of instructions that solve a problem.
Learning programming lets you find out quickly whether you like programming and
whether you have the analytical turn of mind programmers need.
Common terminologies used in computer programming
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Source code
Source code is a program instruction written in a computer programming language to specify the
actions to be performed by a computer.
Pseudo code
Pseudo code is a computer programming language code that resemble plain English that cannot
be compiled but explain a resolution to a problem.
Object code
Object code is a program code that has already been translated into machine readable form
Syntax
Syntax is a set of rules or order to be followed when writing characters in a programming
Debugging
Debugging is a process that involves identifying a problem, isolating the source of the problem,
and correcting the problem by running the program
Algorithm
Algorithm is a list of procedure or instructions or formulas used to solve a problem.
A flow chart
A flowchart is a type of diagram that represents an algorithm, workflow or process.
The flowchart shows the steps as boxes of various kinds, and their order by connecting the boxes
with arrows. This diagrammatic representation illustrates a solution model to a given problem.
Basic Flow chart symbols
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Features of programming language
Simplicity: A good programming language must be simple and easy to learn and use. It should
provide a programmer with a clear, simple and unified set of concepts, which can be easily
grasped. The overall simplicity of a programming language strongly affects the readability of the
programs written in that language, and programs, which are easier to read and understand, are
also easier to maintain. It is also easy to develop and implement a compiler or an interpreter for a
programming language, which is simple. However, the power needed for the language should not
be sacrificed for simplicity.
Naturalness: A good language should be natural for the application area, for which it has been
designed. That is, it should provide appropriate operators, data structures, control structures, and
a natural syntax to facilitate the users to code their problem easily and efficiently.
Abstraction: Abstraction means the ability to define and then use complicated structures or
operations in ways that allow many of the details to be ignored. The degree of abstraction
allowed by a programming language directly effects its writ ability. Object oriented language
support high degree of abstraction. Hence, writing programs in object oriented language is much
easier. Object oriented language also support re usability of program segments due to this
features.
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Efficiency: Programs written in a good programming language are efficiently translated into
machine code, are efficiently executed, and acquire as little space in the memory as possible.
That is a good programming language is supported with a good language translator which gives
due consideration to space and time efficiency.
Structured:- Structured means that the language should have necessary features to allow its
users to write their programs based on the concepts of structured programming. This property of
a moreover, it forces a programmer to look at a problem in a logical way, so that fewer errors are
created while writing a program for the problem.
Compactness: In a good programming language, programmers should be able to express intended
operations concisely. A verbose language is generally not liked by programmers, because they
need to write too much.
Locality:-A good programming language should be such that while writing a programmer
concentrate almost solely on the part of the program around the statement currently being
worked with.
Features of a program
Portability: Portability refers to the ability of an application to run on different platforms
(operating systems) with or without minimal changes. Due to rapid development in the hardware
and the software, nowadays platform change is a common phenomenon. Hence, if a program is
developed for a particular platform, then the life span of the program is severely affected.
Readability: The program should be written in such a way that it makes other programmers or
users to follow the logic of the program without much effort. If a program is written structurally,
it helps the programmers to understand their own program in a better way. Even if some
computational efficiency needs to be sacrificed for better readability, it is advisable to use a more
user-friendly approach, unless the processing of an application is of utmost importance.
Efficiency: Every program requires certain processing time and memory to process the
instructions and data. As the processing power and memory are the most precious resources of a
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computer, a program should be laid out in such a manner that it utilizes the least amount of
memory and processing time.
Structural: To develop a program, the task must be broken down into a number of subtasks.
These subtasks are developed independently, and each subtask is able to perform the assigned
job without the help of any other subtask. If a program is developed structurally, it becomes
more readable, and the testing and documentation process also gets easier.
Flexibility: A program should be flexible enough to handle most of the changes without having
to rewrite the entire program. Most of the programs are developed for a certain period and they
require modifications from time to time. For example, in case of payroll management, as the time
progresses, some employees may leave the company while some others may join. Hence, the
payroll application should be flexible enough to incorporate all the changes without having to
reconstruct the entire application.
Generality: Apart from flexibility, the program should also be general. Generality means that if
a program is developed for a particular task, then it should also be used for all similar tasks of the
same domain. For example, if a program is developed for a particular organization, then it should
suit all the other similar organizations.
Documentation: Documentation is one of the most important components of an application
development. Even if a program is developed following the best programming practices, it will
be rendered useless if the end user is not able to fully utilize the functionality of the application.
A well-documented application is also useful for other programmers because even in the absence
of the author, they can understand it.
Importance of programming
Programming helps the users to understand computers
Knowledge of using and programming computers is essential for scientists and engineers.
Writing simple programs increases the user’s confidential level
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Limitations of programming
It is time consuming and tedious
The user has to master the codes of different languages
It is difficult to make correction when wrong codes are already compiled
The user has to study all the different languages
The Programming Process
Developing a program involves steps similar to any problem-solving task. There are five main
ingredients in the programming process:
1. Defining the problem
2. Planning the solution
3. Coding the program
4. Testing the program
5. Documenting the program
Defining the problem
Specifically, the task of defining the problem consists of identifying what it is you know (input-
given data), and what it is you want to obtain (output-the result). Eventually, you produce a
written agreement that, among other things, specifies the kind of input, processing, and output
required.
Planning the solution
Two common ways of planning the solution to a problem are to draw a flowchart and to write
pseudo code, or possibly both. Essentially, a flowchart is a pictorial representation of a step-by-
step solution to a problem. It consists of arrows representing the direction the program takes and
boxes and other symbols representing actions. It is a map of what your program is going to do
and how it is going to do it.
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Pseudo code is an English-like nonstandard language that lets you state your solution with more
precision than you can in plain English but with less precision than is required when using a
formal programming language. Pseudo code permits you to focus on the program logic without
having to be concerned just yet about the precise syntax of a particular programming language.
However, pseudo code is not executable on the computer.
Coding the program
As the programmer, your next step is to code the program-that is, to express your solution in a
programming language. You will translate the logic from the flowchart or pseudo code-or some
other tool-to a programming language.
As we have already noted, a programming language is a set of rules that provides a way of
instructing the computer what operations to perform. There are many programming languages
such as BASIC, COBOL, Pascal, FORTRAN, and C. You may find yourself working with one
or more of these.
Although programming languages operate grammatically, somewhat like the English language,
they are much more precise. To get your program to work, you have to follow exactly the rules-
the syntax-of the language you are using. Of course, using the language correctly is no guarantee
that your program will work, any more than speaking grammatically correct English means you
know what you are talking about. The point is that correct use of the language is the required
first step. Then your coded program must be keyed, probably using a terminal or personal
computer, in a form the computer can understand.
One more note here: Programmers usually use a text editor, which is somewhat like a word
processing program, to create a file that contains the program. However, as a beginner, you will
probably want to write your program code on paper first.
Testing the Program
Some experts insist that a well-designed program can be written correctly the first time. In fact,
they assert that there are mathematical ways to prove that a program is correct. However, the
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imperfections of the world are still with us, so most programmers get used to the idea that their
newly written programs probably have a few errors. This is a bit discouraging at first, since
programmers tend to be precise, careful, detail-oriented people who take pride in their work.
Still, there are many opportunities to introduce mistakes into programs, and you, just as those
who have gone before you, will probably find several of them.
Eventually, after coding the program, you must prepare to test it on the computer which involves
the following phases:
Desk-checking: This phase, similar to proofreading, is sometimes avoided by the programmer
who is looking for a shortcut and is eager to run the program on the computer once it is written.
However, with careful desk-checking you may discover several errors and possibly save yourself
time in the long run. In desk-checking you simply sit down and mentally trace, or check, the
logic of the program to attempt to ensure that it is error-free and workable.
Translating: A translator is a program that (1) checks the syntax of your program to make sure
the programming language was used correctly, giving you all the syntax-error messages, called
diagnostics, and (2) then translates your program into a form the computer can understand. A by-
product of the process is that the translator tells you if you have improperly used the
programming language in some way. These types of mistakes are called syntax errors. The
translator produces descriptive error messages. For instance, if in FORTRAN you mistakenly
write N=2 *(I+J))-which has two closing parentheses instead of one-you will get a message that
says, "UNMATCHED PARENTHESES." (Different translators may provide different wording
for error messages.) Programs are most commonly translated by a compiler.
A compiler translates your entire program at one time. The translation involves your original
program, called a source module, which is transformed by a compiler into an object module.
Prewritten programs from a system library may be added during the link/load phase, which
results in a load module. The load module can then be executed by the computer.
Debugging; A term used extensively in programming, debugging means detecting, locating, and
correcting bugs (mistakes), usually by running the program. These bugs are logic errors, such as
telling a computer to repeat an operation but not telling it how to stop repeating. In this phase
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you run the program using test data that you devise. You must plan the test data carefully to
make sure you test every part of the program.
Documenting the Program
Documenting is an ongoing, necessary process, although, as many programmers are, you may be
eager to pursue more exciting computer-centered activities. Documentation is a written detailed
description of the programming cycle and specific facts about the program. Typical program
documentation materials include the origin and nature of the problem, a brief narrative
description of the program, logic tools such as flowcharts and pseudo code, data-record
descriptions, program listings, and testing results. Comments in the program itself are also
considered an essential part of documentation. Many programmers document as they code. In a
broader sense, program documentation can be part of the documentation for an entire system.
The wise programmer continues to document the program throughout its design, development,
and testing. Documentation is needed to supplement human memory and to help organize
program planning. Also, documentation is critical to communicate with others who have an
interest in the program, especially other programmers who may be part of a programming team.
And, since turnover is high in the computer industry, written documentation is needed so that
those who come after you can make any necessary modifications in the program or track down
any errors that you missed.
Developing a simple program
To develop and execute a program, the users need to understand three essential elements;
Editing: Where you will create the program source code
Compiling: Where your source code will be converted into a machine code
Executing (Running): Where your program will be run
Example
<html><head><title>Hello World!</title></head>
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<body>
<p>Hello World!
<p>Huh, <em>that's</em>
<a href="http://www.yahoo.com/">Yahoo</a>
</body>
</html>
TOPIC 13: TRENDS IN COMPUTING
Computer integrity and security
Computer integrity refers to the faithfulness or loyality regarding the set laws to computer use
and its resources such as software and hardware devices.
The computer integrity falls into two categories that software integrity and hardware integrity.
In this era of technology, computer law is necessary to clarify actions that fall under the
computer law.
Computer intrusion (computer security threats)
Computer intrusion is a federal crime which needs to be governed by the laws. Such crèmes
include;
Access Device Fraud
Computer Fraud
Communication Interference
Wire and Electronic Communications Interception and Interception of Oral
Communications
Unlawful Access to Stored Communication
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Recording of Dialing, Routing, Addressing and Signaling Information
Computer security threat is any event or action that could lead to damage to computer hardware
and software including the loss of data and information from an information system. These
illegal acts also refer to as computer crimes.
These computer security threats fall under three categories;
Hardware security threats
Software security threats
Network/Internet security threats
Network /Internet security threats
Internet and Network attacks are the criminal offenses done with use of the Internet and
computer networks in connection to hardware and software that are accessible to unauthenticated
users.
Information transmitted over networks has a higher degree of security risk than information kept
on a company‘s premises.
Even a computer not connected into network; an intruder can still have access to the hard drives
and destroy including the data saved on them. Therefore the security of computer hardware and
its components is necessary including protection of overall data.
Below are the most common and most damaging forms of security threats to network and
Internet users and site operators:
Malware
Unwanted programs,
Phishing and identity theft,
Hacking and cyber vandalism
Credit card fraud/theft,
Spoofing (pharming)
Denial of Service
Sniffing, insider attacks,
Poorly designed server and client software
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Every unprotected computer is susceptible to the attack from malicious code.
Malware
Malware is software designed to infiltrate or damage a computer system without the owner's
informed consent. Malware is a general term used by computer professionals to mean a variety
of forms of hostile, intrusive, or annoying software/code.
Unwanted Programs:
These are programs on the internet that install themselves on a computer without the user‘s
consent such as adware, spyware, browser parasite.
Phishing and Identity Theft
Phishing is any deceptive (misleading/false), online attempt by a third party to obtain
confidential information for financial gain.
Hacking and Cyber vandalism:
A hacker is an individual who intends to gain unauthorized access to a computer system. Cyber
vandalism is the act of intentionally destroying computer equipment disrupting, defacing, or
even destroying the site.
Credit Card Fraud/Theft:
Theft of credit card data is one of the most feared occurrences on the Internet. Fear that credit
card information will be stolen frequently prevents users from making online purchases.
Spoofing (Pharming):
Spoofing is also called pharming. It involves redirecting a Web link to an address different from
the Intended one, with the site masquerading as the intended destination.
Denial of Service:
A denial of service attack is an assault whose purpose is to disrupt computer access to an
Internet service such as the Web or e-mail.
Sniffing:
A sniffing is a type of eavesdropping (spying) program that monitors information traveling
over a network.
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Defense against internet and network attacks
Use a firewall
This is a software program that monitors all incoming and outgoing network traffic and allows
only the connections that are known and trusted.
Use antivirus software and keep it up-to-date
The program checks and cures both incoming and outgoing mail in real-time, is simple to install
and use. You only need to choose from three levels of protection.
Regularly check for spyware and adware
Spyware and Adware are files that can be installed on your computer without your permission.
These programs allow hackers to track your behavior on the Internet and retrieve your personal
information such as pin, credit card, phone and social security numbers, passwords, usernames,
etc.
Don’t open unknown email attachments
Don’t open any email attachments unless they are authored by a person or company that you
trust.
Disable hidden filename extensions
Windows operating systems contain an option to “Hide file extensions for known file types”
(enabled by default). Some email viruses take advantage of a hidden file extension. They use an
attachment which may appear to be harmless
Disable Java and ActiveX if possible
Java and ActiveX are used to write code that is executed by Web browsers. Although this code
generally adds useful features, it can be used by hackers, for example, to monitor your Internet
activity. You can disable Java and ActiveX in your browser at the cost of limited interaction with
some websites.
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Turn off your computer or disconnect from the network when not in use
After the session, turn off your computer or otherwise completely disconnect it from the network
when you are not using it. This not only “protects” your computer from Internet security risks, it
forces your ISP to change your computer’s IP address more frequently, thus making it more
difficult for a hacker to get in.
Make regular backups of important data
A hard disk crash or physical theft of your computer results in the loss of all data stored on hard
disk. Keep a copy of important files on removable media such as floppy/ZIP disks or recordable
CD-ROM disks and store these disks somewhere away from the computer.
Route information through a proxy server
Proxy servers are software servers that handle all communications originating from or being sent
to the Internet, acting as a spokesperson or bodyguard for the organization.
Install intrusion detection software;
Intrusion detection software automatically analyzes vulnerabilities, identifies any unauthorized
intrusions, and notifies network administrators of suspicious behavior patterns or system
breaches.
Set of honey pots;
A honey pot is a vulnerable computer that is set up to entice an intruder to break into it.
Encryption all important files
Encryption involves converting data into a form that cannot be easily understood by others.
Use Biometric devices.
This is a form of identity access management and access control which uses measurable physical
and behavioral characteristics of individuals as a way of identifying them as the authentic users.
Examples of biometrics that might be used to authenticate a user include fingerprints, retinal
patterns, or speech/voice.
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Avoid booting computers from infected floppies.
Avoid downloading programs from unknown/unlicensed sources.
Computer virus
A computer virus is a computer program that can copy itself and infect a computer without
permission or knowledge of the user. Viruses attach themselves to executable files that may be
part of legitimate programs. It is a computer code or program specially designed to damage or
cause irregular behavior in other programs in a computer.
Computer viruses are basically designed to carry out two tasks i.e.
To be able to replicate themselves from one computer to another
To be able to position themselves in a computer system and destroy software programs.
Types of computer virus
Computer viruses are categorized into two;
Non-resident viruses
Resident viruses
Non-resident viruses
Nonresident viruses are viruses that which search quickly for other hosts that can be infected.
Resident viruses
Resident viruses are types of viruses that do not search for hosts when they are started instead
they load themselves into memory during execution.
These types of viruses are permanent which dwells in the RAM memory. From there it can
overcome and interrupt all of the operations executed by the system: corrupting files and
programs that are opened, closed, copied, renamed etc.
Examples of resident viruses;
Multipartite Viruses
Direct Action Viruses
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Boot Virus
Directory Virus
Macro Virus
Polymorphic Virus
File Infectors
Network Virus
Multipartite Viruses: Multipartite viruses are distributed through infected media and usually
hide in the memory. Gradually, the virus moves to the boot sector of the hard drive and infects
executable files on the hard drive and later across the computer system.
Direct Action Viruses: The main purpose of this virus is to replicate and take action when it is
executed. When a specific condition is met, the virus will go into action and infect files in the
directory or folder that it is in and in directories that are specified in the batch file.
Boot Virus: This type of virus affects the boot sector of a floppy or hard disk. This is a crucial
part of a disk, in which information on the disk itself is stored together with a program that
makes it possible to boot (start) the computer from the disk.
Macro Virus: Macro viruses infect files that are created using certain applications or programs
that contain macros.
Directory Virus: Directory viruses change the paths that indicate the location of a file. By
executing a program (file with the extension .EXE or .COM) which has been infected by a virus,
you are unknowingly running the virus program, while the original file and program have been
previously moved by the virus. Once infected it becomes impossible to locate the original files.
Polymorphic Virus: Polymorphic viruses encrypt or encode themselves in a different way
(using different algorithms and encryption keys) every time they infect a system.
File Infectors
This type of virus infects programs or executable files (files with an .EXE or .COM extension).
When one of these programs is run, directly or indirectly, the virus is activated, producing the
damaging effects it is programmed to carry out. The majority of existing viruses belongs to this
category, and can be classified depending on the actions that they carry out.
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Network Virus: Network viruses rapidly spread through a Local Network Area (LAN), and
sometimes throughout the internet. Generally, network viruses multiply through
shared resources, i.e., shared drives and folders.
Sources of computer virus
1. Fake games
2. Through use of contaminated diskettes on several computers.
3. Through using pirated software.
4. Through using freeware and shareware from the internet.
5. Since these are free, they are good grounds for distributing viruses.
6. They also in most cases contain bugs which may turn into viruses unintentionally
7. Through software updates most especially over the internet or other networks.
8. Through sharing of data in a network.
How computer viruses spread
Booting a PC from an infected medium such as a floppy.
Executing an infected program.
Opening an infected file.
A virus can only spread from one computer to another when its host is taken to the
uninfected computer.
Viruses can spread to other computers over a network by infecting files on a network file
system or a file system that is accessed by other computers.
Viruses often travel via e-mail attachments. E-mail messages by themselves do not carry
viruses. Only .exe, .com or other types of executable files can carry a virus.
Diskette swapping: using other people’s diskettes for carrying data and programs to and from
affects the computer. Swapping means exchange of materials from one person to another.
Via networking connection: when people are trying to connect to the internet, they acquire
man made virus that affects their programs.
Via file down loading: downloading of files from the internet can spread viruses to your
computer.
Via computer laboratory where different users make unknown applications.
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Via peripheral devices that uses parallel parts of connection.
Symptoms of computer virus
The computer runs slower than usual.
The computer stops responding, or it locks up frequently.
The computer restarts on its own.
Applications on the computer do not work correctly.
Disks or disk drives are inaccessible.
Strange error messages appears on the screen
An antivirus program cannot be installed on the computer, or the antivirus program will not
run.
New icons appear on the desktop that you did not put there, or the icons are not associated
with any recently installed programs.
Strange sounds or music plays from the speakers unexpectedly.
A program disappears from the computer even though you did not intentionally uninstall it
It shuts down unexpectedly or crashes frequently.
It experiences memory problems or runs out of disc space.
Unusual files or directories appear on your system.
Effects of computer virus
1. Some viruses are programmed to damage the computer by damaging programs, deleting files,
or reformatting the hard disk. Others simply replicate themselves and perhaps make their
presence known by presenting text, video, or audio messages.
2. They take up computer memory used by legitimate programs.
3. They can result in system crashes and data loss.
4. They can prevent a computer from booting.
5. The computer may freeze
6. Files on the computer become corrupted
7. Failure to do print jobs
8. Computers may fail to save or accessing a file to save
9. A computer gives un usual sound
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10. It becomes very slow in operation
11. Files go on missing/ cannot be seen
12. Expected files increase in size
13. The computer take time to respond to instructions
14. There will be changes in operation of peripheral devices such as mouse and printers.
15. There will be permanent damages to data files and computer programs.
How to control computer virus
Do not use media like diskettes, backup tapes, CDs from unknown sources.
Scan all foreign media for viruses.
Install antivirus software;
Ensure that the anti – virus software is up to date;
Employ a firewall to protect networks;
Filter all email traffic
Educate all users to be careful of suspicious-mails;
Scan internet downloads;
Don’t run programs of unknown origin;
Make regular backups of critical data. A backup: is a duplicate of a file, program or
disk that can be used if the original is lost, damaged or destroyed.
Other forms of malicious attacks
Time bomb
It is a program code that is activated when it detects a certain condition or event. These events
can be famous days like Valentine, Fools – day.etc.
Droppers
These are programs that have been written to perform useful tasks like compressing
files, previewing video clips, etc. and in the process of performing those tasks; they
introduce viruses in the system.
Bugs:
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A bug is unintentional fault in a program that is normally misinterpreted as a real virus. Moat
complex software in computer systems normally contains bugs. Minor bugs normally cause
simple inconveniences while major bugs can cause loss of data
Adware
It is a program that displays an online advertisement in a banner or pop-up window on
Web pages, email, or other Internet services.
Browser parasite
It is a program that can monitor and change the settings of a user‘s browser.
Spyware
It is a program placed on a computer without the user's knowledge that secretly collects
information about the user e.g. email address, instant messages, etc.
Worms
A worm is a computer program that sits in the computer‘s memory, rewrites
itself continuously into the memory until the system runs out of memory and
crushes. It differs from a virus in that the―reproduced segments keep
communicating with the mother code to function.
Trojan horse
It is a small program code hidden within legitimate software. Unlike a virus or a worm, a Trojan
horse doesn‘t have the ability to replicate itself but it is often a way for viruses or other malicious
code such as bots to be introduced into a computer system. They continue to operate as
legitimate software until at such a time that they are activated to cause trouble
Bots
Are a type of malicious code that can be covertly (secretly) installed on your computer when
attached to the Internet.
Once installed, the bot responds to external commands sent by the attacker, and your computer
becomes a―zombie, and is able to be controlled by an external third party
Meaning of Hacking
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Hacking refers to unauthorized intrusion into a computer or a network. The person engaged in
hacking activities is known as a hacker. Hacker may alter system or security features to
accomplish a goal that differs from the original purpose of the system.
Hackers employ a variety of techniques for hacking, including:
Vulnerability scanner: That is checking computers on networks for known weaknesses
Password cracking: the process of recovering passwords from data stored or transmitted by
computer systems by guessing for the password repeatedly.
Packet sniffer: applications that capture data packets in order to view data and passwords in
transit over networks
Spoofing attack: involves websites which falsify data by mimicking legitimate sites, and they
are therefore treated as trusted sites by users or other programs
Root kit: represents a set of programs which work to subvert control of an operating system
from legitimate operators
Trojan horse: serves as a back door in a computer system to allow an intruder to gain access to
the system later
Viruses: self-replicating programs that spread by inserting copies of themselves into other
executable code files or documents
Denial of service: This is an attempt to make a computer or network resources unavailable to its
intended user.
Key loggers: tools designed to record every keystroke on the affected machine for later retrieval
Meaning of denial of service
Denial-of-service attack is a cyber-attack in which the perpetrator seeks to make a machine or
network resource unavailable to its intended users by temporarily or indefinitely disrupting
services of a host connected to the Internet. Hackers use DoS attacks to prevent legitimate uses
of computer network resources.
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Denial of service attacks are characterized by;
Attempt to flood a network, attempt to disrupt connections between two computers, attempts to
prevent an individual from accessing a service or attempts to disrupt service to a specific system
or person. Those on the receiving end of a denial of service attack may lose valuable resources,
such as their e-mail services, Internet access or their Web server.
Common Denial of Service Attacks
Buffer Overflow
The condition in which data transferred to a buffer exceeds the storage capacity of the buffer and some of
the data overflows into another buffer, one that the data was not intended to go into hence corrupting data
that is already contained in that buffer
Ping of Death
A type of denial of service attack in which the attacker sends a ping request that is larger than
65,536 bytes, which cause a buffer overload on the operating at the receiving end hence crashing the
system.
Smurf Attack
A type of network security breach in which a network connected to the Internet is swamped with replies
to ping requests. A smurf attacker sends PING requests to an Internet broadcast address. These are special
addresses that broadcast all received messages to the hosts connected to the subnet. When a single
attacker sends hundreds or thousands of ping messages the ping replies bring the entire internet service
down.
TCP SYN Attack
In a SYN attack, a sender transmits a volume of connections that cannot be completed. This causes the
connection queues to fill up, thereby denying service to legitimate TCP users.
Teardrop
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A Teardrop is a type of denial of service attack where fragmented packets are forged to overlap each
other when the receiving host tries to reassemble them.
Denial of service attack control
Installing and maintaining anti-virus software
Installing a firewall, and configuration to restrict traffic coming into and leaving your
computer
Follow good security practices for distributing your email address.
Backdoor
A backdoor also known as manhole or trapdoor is a term used to describe a hidden method of
bypassing security to gain access to a restricted part of a computer system. For example, a
programmer may insert a piece of code that would allow them access to a computer or secure
area using a password that only they know.
Spoofing attack (Phishing)
Spoofing is a technique used to gain unauthorized access to computers, whereby the intruder sends
messages to a computer with an IP address indicating that the message is coming from a trusted host. To
engage in IP spoofing, a hacker first use a variety of techniques to find an IP address of a trusted host and
then modify the packet headers so that it appears that the packets are coming from that host.
Spoofing attack is a situation in which one person or program successfully masquerades as
another by falsifying data, thereby gaining an illegitimate advantage.
Forms of spoofing
Caller ID spoofing: This is where callers lie about their identity by presenting false names and
numbers as a tool to defraud other people.
E-mail address spoofing: This is where the email sender altered the information in emails by
hiding the origin of the email
Voice mail spoofing: This is a situation where somebody pretend as if is calling from your cell
phone when it is actually not.
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Global Positioning System (GPS) spoofing: This is a situation where by the GPS sender
deceives a GPS receiver by broadcasting incorrect GPS signals, structured to resemble a set of
normal GPS signals, or by rebroadcasting genuine signals captured elsewhere or at a different
time.
Computer crime
Computer crimes are criminal activities which involve the use of information technology to gain
an illegal or unauthorized access to a computer system with the intent of damaging, deleting, or
altering computer data. They also include activities such as electronic frauds, misuse of devices,
identity theft, and data as well as system interference.
Computer crimes may not necessarily involve damage to physical property. They rather include
the manipulation of confidential data and critical information. They involve activities like
software theft, wherein the privacy of users is hampered.
There are four basic categories are utilized in describing computer crime. These are: theft,
fraud, copyright infringement and attacks.
Different forms (types) of computer crimes
Child pornography - Making or distributing child pornography.
Cracking - Breaking or deciphering codes that are being used to protect data.
Cyber terrorism - Hacking, threats, and blackmailing towards a business or person.
Cyber bully or Cyber stalking - Harassing others online.
Creating Malware - Writing, creating, or distributing malware (e.g., viruses and spyware.)
Denial of Service attack - Overloading a system with so many requests it cannot serve normal
requests.
Espionage - Spying on a person or business.
Fraud - Manipulating data, e.g., changing banking records to transfer money to an account.
Harvesting - Collect account or other account related information on other people.
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Identity theft - Pretending to be someone you are not.
Intellectual property theft - Stealing practical or conceptual information developed by another
person or company.
Phishing - Deceiving individuals to gain private or personal information about that person.
Salami slicing - Stealing tiny amounts of money from each transaction.
Scam - Tricking a person into believing something that is not true.
Spamming - Distributed unsolicited e-mail to dozens or hundreds of different addresses.
Spoofing - Deceiving a system into thinking you are someone you really are not.
Unauthorized access - Gaining access to systems you have no permission to access.
Wiretapping - Connecting a device to a phone line to listen to conversations.
Sniffing: The act of intercepting internet protocol packets while getting transferred on a network
Eavesdropping: The act of secretly listening to the private conversation of others without their
consent
Smishing: The act of using cell phone text message to lure people to provide personal
information such financial ID, driving license number etc.
Safeguarding against computer crimes
Use of log files
Data encryption
Use of firewall
Use of updated antivirus software
Use of Biometric devices
Use of password
Putting up physical security mechanism such as CCTV cameras and sensors
Employing system administrators to centrally manage system resources
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Computer protection (Computer security system)
Computer system security is the ability of a computer system to protect information and system
resources with regards to confidentiality and integrity. It refers to all processes and mechanisms
by which computer based equipment, information and services are protected from unauthorized
access or destruction including unplanned events and disasters.
Forms of computer security system
There are two forms or categories of computer security systems;
Physical security
Data security
Physical security is the protection of personal programs, networks and data from physical
circumstances and events that could lead to damage. The protection includes protection from
fire, natural disasters, buglers, theft, vandalism and terrorism.
In order to protect the physical equipments, the following physical security access control
measures must be put in place;
Use physical access controls such as locked doors and windows.
Use cables to lock the equipment to desk, cabinet or floor.
Install alarm systems to warn you in case of any intrusion
Use passwords, and biometric devices.
Install surveillance cameras to help you in easy monitoring of the hardware
Putting up strong burglar poof doors and windows to avoid thieves
Ensure that fire extinguisher is fixed in the computer lab in case of any emergency fire
outbreak
Consider installing a security alarm at a strategic point in case of a breakage.
Do not welcome strangers into the computer room.
Employing security guards to the entrance of the facilities
A possessed object is any item that one must carry to gain access to a computer or
computer facility such as card key to secure physical area
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Data security refers to the methods of protecting a database from destructive forces and
unwanted actions of unauthorized users. For data protection to be ensured the user must employ
both hardware and software based security mechanisms such as;
Keep a copy of your data off site in case of any firebreak.
Make regular backups of critical data. A backup: is a duplicate of a file, program or disk
that can be used if the original is lost, damaged or destroyed
Protect data files by using password mechanism
Install intrusion detection software to provide extra protection against hackers and other
intruders.
Use data masking. Data masking is the process of obscuring a specific data within a
database table to ensure that data is maintain and sensitive information is not exposed to
unauthorized user.
Install reliable antivirus programs on your computer system and update it regularly.
You can use steganography program to hide data inside another data.
Use encryption mechanism. Encryption is the process of transforming plain text or data
into cipher (unreadable) text that cannot be read by anyone other than the sender and the
receiver. It is a process of covering readable data into unreadable characters to prevent
unauthorized access.
Install a firewall-The key defense against Internet attackers is an Internet firewall.
Avoid e-mail Attachments from Unknown Sources.
Avoid booting computers from infected floppies.
Avoid downloading programs from unknown/unlicensed sources.
Computer ethics
Ethics is a set of moral principles that govern the behavior of a group or individual. Therefore, computer
ethics is set of moral principles that regulate the use of computers. Some common issues of computer
ethics include intellectual property rights (such as copyrighted electronic content), privacy concerns, and
how computers affect society.
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As technology advances, computers continue to have a greater impact on society. Therefore, computer
ethics promotes the discussion of how much influence computers should have in areas such as artificial
intelligence and human communication. As the world of computers evolves, computer ethics continues to
create ethical standards that address new issues raised by new technologies.
Ethical issues arising from the development and wide-spread use of ICT are of increasing concern.
Prominent examples include the limitations of privacy in social network sites, ownership and control of
data by search providers, the limitations on the use of large-scale public databases or ICT systems or the
possibility of moral agency by autonomous systems.
Common ethical issues in ICT
The most common ethical issues that need to be address in the ICT industry include;
Label issue: Libel is the publication of a false statement that injuries one’s business or personal
reputation.
Plagiarism: Plagiarism means using someone intellectual property such as ideas and written
works and claim that ideas is yours
Software piracy: Software piracy refers to the act of installing a copy of software into your
computer without authorization.
Misuse: Misuse is the use of the harmful acts such as hacking, spamming, cracking etc.
Copyright infringement: copyright infringement refers to the act of copying intellectual
property without the written permission from the copyright owner.
The rights owned by the owner of the copyright are:
The right to modify the work to create a new work
The right to distribute the work to the public by sale
The right to display a copy of the work directly to the public by posting it on the internet,
hanging it on public places, putting it on films or movies
Computer ethics and integrity
Computer ethics are moral guidelines or codes of conduct that govern the use of
computer and information systems.
On the other side computer integrity refers to the loyalty or faithfulness regarding
the set laws to computer use.
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Codes of conduct
Codes of conduct are written guidelines that help to determine whether a specific action is ethical
or unethical.
Computer ethical codes of conduct
Computers should not be use to Harm Other People.
Computers should not be use to Interfere with Other People's Computer Work.
Users should not snoop around in Other People's Computer Files.
Computers should not be use for stealing.
Computers should not be use to Bear False Witness.
Users should not copy or use Proprietary software for which you have not paid.
Thou Shall Not Use Other People's Computer Resources without Authorization or Proper
Compensation.
Thou Shall Not Other People's Intellectual Output.
Computer users should think about the social consequences of the program one is
designing.
Users should always use computers in consideration and respect for others.
Unethical computer codes of conduct
Modifying people’s information on the internet without authorization
Selling someone information to other parties without the owner’s permission
Using someone information or resources without authorization
Stealing of computer software
Sending or posting flames which are so abusive or insulting messages
Invasion of privacy
Using capital letters which is equivalent to shouting
Computer privacy
Privacy is the moral right of individuals to be left alone, free from surveillance or
interference from other individuals or organizations, including the state.
Information Privacy refers to the right individuals, companies or organizations have
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to deny or restrict the collection and use of information about them.
Different aspects of information privacy and violation
The use of Global Positioning system (GPS) and (RFID) technologies has led to the
violation of information privacy for example GPS which is use to tack the movement of
people by mobile signals, and the use of Radio frequency identification (RFID) enable
companies to track their customer’s purchases and profile their behaviors.
Online services such as flight tickets, hotel bookings, and internet banking has made
people to provide some important private information to other organizations.
Online social services such as email, what sap, twitter, face book etc are essential
communication tools these days but they are not secure ways to protect privacy.
Individual’s personal data these days can be traced and gained through databases,
spyware and cookies which give providers wider chances to access personal information.
A cookie is a small text file that a Web server stores on your computer that allows a
site to track the actions of its visitors. E-commerce, Webcasting, and other Web
applications often rely on cookies to identify users and track information about
viewers, customers, and subscribers.
A cookie resides on an individual’s hard drive, but does not interact with other
information store on the system.
Intellectual property rights
Intellectual property is a category of property that includes intangible creations of the human intellect,
and primarily encompasses copyrights, patents, and trademarks. It also includes other types of rights, such
as trade secrets, publicity rights, moral rights, and rights against unfair competition.
A right that is had by a person or by a company to have exclusive rights to use its own plans, ideas, or
other intangible assets without the worry of competition, at least for a specific period of time.
Intellectual property is divided into two categories:
Industrial Property includes; patents for inventions, trademarks, industrial designs and
geographical indications.
Copyright covers literary works (such as novels, poems and plays), films, music, artistic
works (e.g., drawings, paintings, photographs and sculptures) and architectural design.
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Types of intellectual property
Copyright
Copyright is a legal term used to describe the rights that creators have over their literary and
artistic works. Works covered by copyright range from books, music, paintings, sculpture and
films, to computer programs, databases, advertisements, maps and technical drawings.
Patents
A patent is an exclusive right granted for an invention. Generally speaking, a patent provides the
patent owner with the right to decide how - or whether - the invention can be used by others. In
exchange for this right, the patent owner makes technical information about the invention
publicly available in the published patent document.
Trademarks
A trademark is a sign capable of distinguishing the goods or services of one enterprise from
those of other enterprises. Trademarks date back to ancient times when artisans used to put their
signature or "mark" on their products.
Copy right law in Uganda
Copyright law in Uganda is currently is governed by; the Cop yright and Neighbouring Act, 2006
and the Copyright a nd Neighbouring Rights Regulations, 2010 .
The Act provides that NO person of any kind shall produce, reproduce, distribute, broadcast,
make available to the public, sale or offer for sale, lease or rent out or make public performances
or import for distribution …audio visual recordings in Uganda except under a licence issued by
the owner of the neighbouring rights or a Collecting society.
Computers and society
Impacts of computer technology in society
Computer technology has open opportunity for new job creation such as software
developers, system administrators, computer operators, database administrators etc.
With many improvements in computer technology, it has contributed to job replacement
for instance many computer illiterates have been replaced by skilled computer personnel.
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Besides that, the introduction of computer technology has led to job replacement for
example many security personnel have been replaced by the use of CCTV, and sensors
technologies
Computer technology in automation has greatly improved on the quality and quantity of
products being produced.
Introduction of computer technology has also greatly affected the nature of people work
for example secretarial work was done by the use of typewriter has been replaced with
the use of application software programs and the use of non impact printers.
The introduction of computer technology has open more avenues for computer crimes
such as electronic fraud, misuse of devices, identity theft etc.
The introduction of digital forensic is helping in recovery and investigation of material
found in digital devices related to computer crime.
The introduction of computer technology has open more avenues for computer crimes
such as electronic fraud, misuse of devices, identity theft etc.
The introduction of digital forensic is helping in recovery and investigation of material
found in digital devices related to computer crime.
On environment, the computer technology has enabled national meteorological centers
and the ministry of environment to improve disaster warnings and relief.
Computer technology has led to the improvement in agricultural and forestry sectors by
carrying out research towards better farming methods and mechanization.
The use of computer technology has brought about some negative impacts to the
environment such as:
Pollutant manufacturer of hardware equipments
Improper disposal of e-waste
The use of high energy consumption devices leading to global warming
Deforestation resulting from planting ICT masts, satellites, and setting up
of ICT related companies and factories
The use of various computer technologies have greatly contributed to many health related
problems such as:
Headache as a result of excessive use of computers
Neck pain as a result of improper sitting posture
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Infections a s a result of germs from dirty keyboard, mouse, and the working area.
Repetitive stress injury resulting from wrist, hand, arm muscle strain and neck
Eye strain resulting from flickering and too much brightness of the monitor
Backache resulting from improper sitting and bad chair design.
Emerging technologies
Emerging technologies are technologies that are perceived as capable of changing the status
quo. These technologies are generally new but include older technologies that are still
controversial. Prediction suggests that with the rapid advancement in information and
communication technology more new technologies and computer related hardware devices,
software and applications are emerging up which will bring a lot of impacts in all aspects of life.
Lists of Emerging technologies
Artificial intelligence
Artificial Intelligence is a group of related technologies that attempt to develop machines to
emulate human like qualities such as learning, reasoning, communicating, seeing and hearing.
Three Dimensional (3D) optical storage media
This is a form of optical data storage in which data and information can be written, read and
recorded with three dimensional resolutions opposed by two dimensional resolution media such
as CD and DVD.
Fourth generation (4G0 cellular communication
4G cellular communication is a system that provides mobile ultra-broad band internet access to
laptops, USB wireless modems, smart phones, and to other mobile devices. It is a successor of
3G cellular communication.
Radio Frequency identification
Radio Frequency identification is the use of a wireless non-contact system that uses radio
frequency electromagnetic fields to transfer from a tag attached to an object for the purpose of
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automatic identification and tracking.
Three Dimensional (3D) printing
3D printing is a combined system with Internet technology allow for digital blueprints of
virtually material products to be sent instantly to another person to be produced on the spot,
making purchasing a product online immediately.
Distributed ledger technology
Distributed ledger is a technology which provides transparent and immutable lists autonomous
transactions through the use of smart contracts. A smart contract is a vending machine that holds
goods until money has been received and then the goods are released to the buyer. The machine
holds the property and is able to enforce the contract. There were two main issues that needed to
be addressed before smart contracts could be used in the real world. The first one is the control
of physical assets by smart contract to be able to enforce agreements. Secondly, the last of
trustworthy computers that is reliable and trusted to execute the contract between two or more
parties.
Application areas of Emerging technologies
The use of mobile phones allows transfer or transaction of money from any bank or credit
line and vice versa.
The application of Radio Frequency identification in the area of identification and
tracking of assets use by many legal firms
One of the most common applications of car phones is in charging iphones and other
tablets freeing many people from the worry of charging their devices.
The application of digital forensics in criminal investigation before a criminal is
presented before the court of law.
The application of smart contract machine for holding goods until money has been
received and then the goods are released to the buyer by business companies.
Advantages of Emerging technologies
Easy Access to Information
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It has become pretty easy to get access to relevant information at anytime and anywhere. This
has been possible because of modern technologies like broadband internet.
Lots of data is being published and indexed online, sites like Wikipedia and YouTube have great
original content that is regularly used for research or entertainment.
With smart gadgets like the iPad, iPhone, Galaxy tablets, etc., users can easily have access to a
vast amount of information wherever they are through the use of the internet on these devices.
These smart gadgets make it easy to access the internet anywhere, and this simplifies the way we
get information.
Encourages Innovation and Creativity
Since technology seems infinite, it sparks the brain to work to its full potential. In the past, it
used to be very difficult to start a business, one had to have lots of capital, and they even had
limited access to business information.
Today, it is simple to start a business while at home. On this platform, creative developers post
projects to seek funding from the community; this helps them generate capital for their ideas
which later leads to the creation of new jobs and further innovation of technology. The other
creative works which have been facilitated by modern technology include Google, Apple, Face
book, Microsoft, Amazon, etc
Improved Communication
Communication is like water to life; it is essential to growth, we cannot progress without
communication. Modern technology has blessed us with advanced communication technology
tools. These include e-fax, electronic mail, mobile phones, video conferencing, instant text
messaging applications, social networking, etc.. All these modern communication technology
tools have simplified the way humans and businesses communicate.
The Convenience of Traveling/ Ease of Mobility
Modern transportation technology makes it very easy to travel long distances. Transport is a very
important both in our lives and in the business world. Transportation technology has evolved
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with years. In the past, it used to be slow and expensive to move long distances. Nowadays, we
can cover a 10 miles distance within a few minutes using electric trains, airplanes or cars.
Improved Housing and Lifestyle
This is another excellent way how modern technology has simplified our lives. If you compare
the type of housing we used in 1900 and the architecture of houses today, the difference is
enormous. New architectural technology has improved the kinds of home we build. People with
money can afford floating homes, and glass homes or people with smaller means can make tiny
houses or mobile homes. Most of the items in our houses are now automated, for example, doors
use fingerprints, key cards, or Bluetooth on our mobile. Security has also increased at home with
the evolution of more robust integrated security system.
Improved Entertainment
Modern technology has played a significant role in changing the entertainment industry. Home
entertainment has improved with the invention of video games, advance music systems and
visual systems like smart televisions, which can connect live to the internet so that a user can
share what they’re watching with friends. Easy access and storage of music are ever present,
services like iTunes allow users to purchase and download music on their players at a small cost,
and this is a win-win situation for both musicians and the users. Additionally, bars, clubs, and
amusement parks have all benefited from advancements in technology. We can see things in 3D,
ride the highest roller coaster or be served by a robot at the bar, all possible through modern
technology.
Efficiency and Productivity
Modern technology has helped businesses increase production. Humans are slow, and sometimes
they fail to deliver on time and quality. Many companies have integrated modern technology in
their production line, increasing output and allowing for more consistent quality.
Convenience in Education
Learning is a process, and it is part of our daily lives. Modern technology has made it simple for
students to learn from anywhere through online education and mobile education. Also, students
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now use modern technology in classrooms to learn more effectively. For example, students use
tablets to share visual lessons and examples with peers in the classroom; this has made learning
more convenient and fun. Also, new modern educational technologies support individual
learning which gives students a chance to learn on their own with no need for tutors.
Social Networking
Modern technology has made it simple to discover our old friends and also discover new people
to network with; this is a benefit to both individuals and businesses. Many businesses have
embraced social networking technology to interact with their customers. Users of social
networks can share information with friends, live chat with them and interact in all sorts of ways.
Benefits to the Health Industry
Today most hospitals have implemented modern technology in surgical rooms, and this has
reduced mistakes made by doctors. Humans can easily make mistakes because of work overload
and stress factors. Additionally, the development community has developed health apps that
enable us to monitor our health, weight or fitness. These applications are used on mobile phones,
so users have access anytime.
Disadvantages of Emerging technologies
Increased Loneliness
Social Isolation is on the increase, people are spending more time playing video games, learning
how to use new modern technologies, using social networks and they neglect their real life.
Technology has replaced our old way of interacting. If a user can easily interact with 100 friends
online, they will feel no need to go out to make new friends which at a later stage can lead to
loneliness.
Job Loss
Modern technology has replaced many human jobs; robots are doing the jobs which used to be
done by humans. Many packing firms have employed robots on production lines to increase
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production and efficiency, this is good news for businesses because it helps them make more
money and serve customers, but it is bad news for employees because they may become
redundant.
Excessive dependency:
Increased dependencies on modern tools and applications like calculators and spelling checkers
have reduced creativity. This affected the way we use our brains. Also depending on machines
and modern transportation put people at a distinct disadvantage, because they became less self –
reliant.
Security
Thankfully advances in technology have aided security, however, due to these advances;
everything is connected to the internet in some way. Our financial accounts, our photos, our cars,
mobile phone, everything touches the internet at some time. Due to the network of worldwide
devices and systems, many have fallen prey to an identity thief, hacked accounts by some
mischievous hacker. The road to recovery from these types of attacks can be extremely long and
painstaking.
World Destruction/Advanced Weapons
Modern technology has been the main aid in the increasing of endless wars. It aids the
manufacturing of modern war weapons. So when these weapons get into the hands of criminals,
they will use them for their selfish reasons. To add, these weapons often severely damage the
natural earth, making some areas uninhabitable.
High Maintenance costs
It is expensive to buy technology, but it is also costly to maintain it. Many small businesses can
not afford the cost of hiring a full-time technical person, so they resort to monthly tech
contractors who charge them for work done. If business technology tools like computers are not
well maintained, their performance will decrease and the process of buying new computers or
any other business technology can even be more expensive.
System Analysis
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Systems analysis is a problem-solving method that involves looking at the wider system,
breaking apart the parts, and figuring out how it works in order to achieve a particular goal.
A system is a set of components that interact to accomplish some purpose. For example, a computer
system contains processors, memory, electrical pathways, a power supply. others include College
system, Economic system, Language system, a Business and its parts - Marketing, Sales, Research,
Shipping, Accounting, Government.
The first step in solving a problem that involves a system is analyzing that system. This involves
breaking it down into the parts that make it up, and seeing how those parts work together.
Sometimes figuring out how a system works can involve turning off parts of the system and
seeing what happens, or changing parts of the system and seeing what the result is. If you change
what goes into a system, how does it change what comes out? Basically, systems analysis
involves techniques that allow you to understand how a system works.
Definition of terminologies
System: A system is a set of components that interact to accomplish some purpose.
Information System is interrelated components working together to collect, process, store, and
disseminate information to support decision making, coordination control analysis and
visualization in an organization.
Information: Data that have been transformed into meaningful and useful form to human
beings.
Data: Streams of raw facts representing events occurring in organizations.
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InputProcessing
Classify
Arrange
OutputORGANIZATION
FEEDBACK
INFORMATION SYSTEM
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Input: The capture or collection of raw data from within the organization or from its external
environment.
Processing: The conversion, manipulation, and analysis of raw input into a form that is more
meaningful to humans.
Output: The distribution of processed information to the people or activities where it will be
used.
Feedback: Output that is returned to the appropriate members of the organization to help them
evaluate or correct the input.
Computer-Based I.S. (CBIS): I.S. that rely on computer hardware and software for processing
and disseminating information.
System Analysis - Process of gathering and interpreting facts, diagnosing problems, and using the
facts to improve the system.
System analyst is an information specialist who performs systems analysis, design, and
implementation.
Systems Design - Process of planning a new system to replace or complement the old. Analysis
specifies what the system should do and design states how to achieve the objective.
Systems development Life Cycle (SDLC) is a series of stages applied to information system
development projects ensuring that all functional and user requirements, strategic goals and
objectives are met
Importance of system analysis
It helps in evaluating system request
It provides various experienced and knowledge at the time of evaluating system request
one person view point cannot affect the committee decisions
Phases of system analysis
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These are series of stages applied to information system development projects ensuring that all
functional and user requirements, strategic goals and objectives are met. Theses phases are called
systems development Life Cycle (SDLC) which include;
Preliminary investigation
System analysis
System design
System coding
System Testing
System implementation
System maintenance
The different phases of system development life cycle are shown in Fig. 1.2 below.
System Study
Maintenance
Feasibility Study
Software
Implementatio
n DevelopmentSystem
Analysis
Life Cycle
Testing
System Design
Coding
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Preliminary System Study
Preliminary system study is the first stage of system development life cycle. This is a brief
investigation of the system under consideration and gives a clear picture of what actually the
physical system is? In practice, the initial system study involves the preparation of a ‘System
Proposal’ which lists the Problem Definition, Objectives of the Study, Terms of reference for
Study, Constraints, and Expected benefits of the new system, etc. in the light of the user
requirements.
The system proposal is prepared by the System Analyst (who studies the system) and places it
before the user management. The management may accept the proposal and the cycle proceeds
to the next stage. The management may also reject the proposal or request some modifications in
the proposal. In summary, we would say that system study phase passes through the following
steps:
Problem identification and project initiation
Background analysis
Inference or findings (system proposal)
Feasibility Study
System Analysis
Systems analysis is a process of collecting factual data, understand the processes involved,
identifying problems and recommending feasible suggestions for improving the system
functioning.
This involves studying the business processes, gathering operational data, understand the
information flow, finding out bottlenecks and evolving solutions for overcoming the weaknesses
of the system so as to achieve the organizational goals.
System Analysis also includes sub-dividing of complex process involving the entire system,
identification of data store and manual processes.
The major objectives of systems analysis are to find answers for each business process: What is
being done How is it being done, who is doing it, When is he doing it, Why is it being done and
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How can it be improved? It is more of a thinking process and involves the creative skills of the
System Analyst.
It attempts to give birth to a new efficient system that satisfies the current needs of the user and
has scope for future growth within the organizational constraints. The result of this process is a
logical system design. Systems analysis is an iterative process that continues until a preferred
and acceptable solution emerges.
System Design
Based on the user requirements and the detailed analysis of the existing system, the new system
must be designed. This is the phase of system designing. It is the most crucial phase in the
developments of a system. The logical system design arrived at as a result of systems analysis is
converted into physical system design. Normally, the design proceeds in two stages:
Preliminary or General Design
Structured or Detailed Design
Preliminary or General Design: In the preliminary or general de-sign, the features of the new
system are specified. The costs of implementing these features and the benefits to be derived are
estimated. If the project is still considered to be feasible, we move to the de-tailed design stage.
Structured or Detailed Design: In the detailed design stage, computer oriented work begins in
earnest. At this stage, the design of the system becomes more structured. Structure design is a
blue print of a computer system solution to a given problem having the
System Coding
The system design needs to be implemented to make it a workable system. This demands the
coding of design into computer understandable language, i.e., programming language. This is
also called the programming phase in which the programmer converts the program specifications
into computer instructions, which we refer to as programs. It is an important stage where the
defined procedures are transformed into control specifications by the help of a computer
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language. The programs coordinate the data movements and control the entire process in a
system.
System Testing
Before actually implementing the new system into operation, a test run of the system is done for
removing the bugs, if any. It is an important phase of a successful system. After codifying the
whole programs of the system, a test plan should be developed and run on a given set of test
data. The output of the test run should match the expected results. Sometimes, system testing is
considered a part of implementation process.
Using the test data following test run are carried out:
Program test: When the programs have been coded, compiled and brought to working
conditions, they must be individually tested with the prepared test data. Any undesirable
happening must be noted and debugged (error corrections)
System Test: After carrying out the program test for each of the programs of the system and
errors removed, then system test is done. At this stage the test is done on actual data. The
complete system is executed on the actual data. At each stage of the execution, the results or
output of the system is analyzed. During the result analysis, it may be found that the outputs are
not matching the expected output of the system. In such case, the errors in the particular
programs are identified and are fixed and further tested for the expected output.
When it is ensured that the system is running error-free, the users are called with their own actual
data so that the system could be shown running as per their requirements.
System Implementation
After having the user acceptance of the new system developed, the implementation phase begins.
Implementation is the stage of a project during which theory is turned into practice. The major
steps involved in this phase are:
Acquisition and Installation of Hardware and Software
Conversion
User Training
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Documentation
System Maintenance
Maintenance is necessary to eliminate errors in the system during its working life and to tune the
system to any variations in its working environments. It has been seen that there are always some
errors found in the systems that must be noted and corrected. It also means the review of the
system from time to time. The review of the system is done for:
Knowing the full capabilities of the system
Knowing the required changes or the additional requirements
Studying the performance
N.B. If a major change to a system is needed, a new project may have to be set up to carry out
the change. The new project will then proceed through all the above life cycle phases.
Computer professions (Careers in ICT industry)
This refers to the job titles or professions related to information communication
(ICT). The high growth rate in ICT industry has resulted into many new kinds
of jobs and careers.
Different careers in the field of computing
Computer operators
Responsibilities
Entering data into the computer for processing
Keeping up-to-date records of all information processing activities
Computer technician
Computer technician is a person responsible for the maintenance, upgrading and
repairing of computers and related devices
Responsibilities
Troubleshooting computer hardware and software related problems
Assembling and upgrading computers and their components
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Ensuring that all computer related accessories such as printers, modems, storage media
and devices are in a good working condition.
Systems analyst
This is a person who is responsible for analyzing a company‘s needs or problems, then
designs and develops a computer based information system to help prevent the problem.
Responsibilities
Reviewing the current manual or redundant information system and making
recommendations on how to replace it with a more efficient one.
Working with programmers to construct and test the system.
Coordinating training for users on how to use the new system
Computer programmer
Responsibilities
Writing application programs or system programs.
Customizing commercial application package to suite the organization needs.
Testing, debugging, installing and maintaining programs developed or
customized for the organization.
Software developer (engineer)
Software developer is a person who is skilled in software development and
technical operation of computer hardware.
Responsibilities
Developing system and application software
Developing user and technical documentations for the new software.
Maintaining and updating the software to meet day to day requirements while
overcoming challenges.
Computer engineer
Computer engineer is a technical person with skills and knowledge of designing and
developing computer components such as storage devices, motherboards, and other
electronic components.
Responsibilities
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Determine the electrical power requirement of each computer component.
Re – engineer computer components to enhance its functionality and efficiency.
Design and develop engineering and manufacturing computer controlled devices such
as robots.
Information systems manager
Responsibilities
He controls, plans, staffs, schedules and monitors all the activities of the ICT
department in the organization.
Test the impact that an alternative course of action might have on the business.
Ensures that all tasks in the IT department are done correctly and on time in order to
support business planning, control and decision making process.
Prepares budgets for the ICT department.
Keeps the department‘s inventory records up-to-date.
Managing the human resource within the ICT department.
Database administrators (DBA)
Responsibilities
Designing and developing database applications for the organization.
Setting up security measures needed to control access to data and information.
Keeping the database up-to-date by adding new records, modifying or deleting un
necessary records.
Computer trainer/Instructor/Teacher
Due to the dynamic nature of computers and information technology, there is a high
demand for qualified ICT trainers.
Responsibilities
Training people on how to use a computer and various application programs.
Developing training reference materials
Guiding learners on how to acquire knowledge through carrying out research.
Advising the learners on the best career opportunities in the broad field of ICT.
Preparing learners for ICT examinations.
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Website administrator /Webmaster
Responsibilities
Developing and testing websites
Maintaining, updating and modifying information on the websites to meet new
demands by the users.
Monitoring the access and use of internet connection by enforcing security measures.
Downloading information needed by an organization or institution from the internet
websites.
Computer graphics designer
This is a professional responsible who designs and creates either graphics or 3D animations for
software programs, games, movies by people. This person must have a good understanding of
graphic software’s such as Adobe Photoshop, Adobe Illustrator, etc
Network administrator
Responsibilities
This is a professional person responsible for designing, setting up and maintaining a
network
Monitoring the network resources
Troubleshooting network related problems
Secretary
A secretary is a person who uses computers to keep all the necessary
information instead of keeping paper files
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Abbreviation and Glossary
COMPUTER ABBREVIATIONS AND GLOSSARY
Aa
AD Analog to Digital
AC Alternating Current
ACC Accumulator
ACIA Asynchronous Communication Interface Adapter
ACK Acknowledge
ACR Audio Cassette Recorder
ACU Automatic Calling Unit
ADC Analog to Digital Converter
ADP Analog Data Processing
AI Artificial Intelligence
ALGOL Algorithmic Language
ALU Arithmetic Logic Unit
ANSI American National Standards Institute
APL A Programming Language
APT Automatic Programmed Tools
ASCII American Standard Code for Information Interchange
ASIC Application Specific Integrated Circuits
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ASR Automatic Send or Receive
ATC Automatic to Copy
ATE Automatic Test Equipment
ATM Automatic Teller Machine
ATP Apple Transaction Protocol
ARPA Advanced Research Projects Agency
AMD Advanced Micro Devices
Bb
BASIC Beginners All-purpose Symbolic Instruction Code
BBS Bulletin Board System
BCC Block Character Check
BCD Binary Code Decimal
BCHC Bose- Chandhuri-Hocquenghem Code
BCS British Computer Society
BIM Beginning of Information Mark
BIOS Basic Input/output System
BNF Backus-Naur Form
BOS Basic Operating System
BOT Beginning Of Tape
BPI Bits per Inch
BSI British Standard Institute
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BSC Binary Synchronous Communications
BTAM Basic Telecommunications Access Method
Cc
CAD Computer Aided Design
CAI Computer Aided Instruction
CAL Computer Aided Learning
CAM Computer Aided Manufacturing
CAM Content Addressable Memory
CAT Computer Aided Training
CAT Computer Aided Testing
CBL Computer Based Learning
CBMS Computer Based Message System
CBT Computer Based Training
CCD Charge Coupled Device
CCP Command Console Processor
CD Compact Disk
CD-ROM Compact Disk-Read Only Memory
CM Central Memory
CPE Central Processing Element
CPU Central Processing Unit
CGA Color Graphics Adapter
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CIM Computer Input from Microfilm
CIR Current Instruction Register
CISC Complex Instruction Set Computer
CM Central Memory
CMI Computer Managed Instruction
CML Computer Managed Learning
CMOS Complementary Metal Oxide Semiconductor
CNC Computer Numeric Control
COBOL Common Ordinary Business Oriented Language
CODEL Coder/Decoder
CSMA-CD Carrier Sense Multiple Access-Collision-Detection
COM Computer Output on Microfilm
COMAL Common Algorithmic Language
CP/M Control Program for Micro computers
CP/M Control Program/Monitor
CORAL Common Real time Applications Language
CP Card Punch
CPM Critical Path Method
CPI Characters per Inch
CPS Character per Second
CR Carriage Return / Card Reader
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CRC Cyclic Redundancy Check
CR/LF Carriage Return/Link Feed
CRT Cathode Ray Tube
CSM Combined Symbol Matching
CTRL Control
CTS Clear To Send
CU Control Unit
CUG Closed User Group
CAR Current Address Register
CIR Current Instruction Register
CWP Communicating Word Register
CD-R Compact Disk-Recordable
CD-RW Compact Disk-Rewritable
CVP Computer Virus Protection
CC Carbon Copy
CMY Cyan Magenta and Yellow
CLI Command Line Interface
Dd
3D Three Dimensional
DAC Digital to Analog Converter
DAMA Demand Assigned Multiple Access
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DASD Direct Access Storage
DBA Database Administrator
DBMS Database Management System
DC Direct Current
DCD Data Carrier Defect
DCE Data Communications Equipment
DD Double Density
DDC Direct Digital Control
DDE Direct Data Entry
DD/D Data Dictionary/Directory
DDL Data Description Language
DDP Distributed Data Processing
DES Data Encryption Standard
DFD Data Flow Diagram
DIB Data Input Bus
DIN Deutsche Industry Norm
DIP Dual Inline Package
DIANE Direct Information Access Network for Europe
DMA Direct Memory Access
DML Data Manipulation Language
DOR Digital Optical Reading
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DOS Disk Operating System
DP Data Processing
DPI Dots per Inch
DPM Data Processing Manager
DRAM Dynamic Random Access Memory
DRO Destructive Readout
DSR Data Set Ready
DSW Device Status Word
DTE Data Terminal Equipment
DTP Desk Top Publishing
DTR Data Terminal Ready
DVD Digital Video Disks
DVD Digital Versatile Disk
DNS Domain Name System
DSL Digital Subscriber Line
DARPA Defense Advanced Research Projects Agency
Ee
EDVAC Electronic Discrete Variable Automatic Computer
EAPROM Electrically Alterable Programmable-Read Only Memory
EAROM Electrically Alterable Read Only Memory
EBCDIC Extended Binary Coded Decimals Interchange Code
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EBNF Extended Backups Naur Form
EBR Electron Beam Recording
ECL Emitter Coupled Logic
EDP Electronic Data Processing
EDS Exchangeable Disk Storage
EEPROM Electronically Erasable Programmable Read Only Memory
EEROM Electronically Erasable Read Only Memory
EFT Electronic Funds Transfer
EFTPOS Electronic Fund Transfer Point of Sale
EGA Enhanced Graphics Adapter
EIA Electronically Industry Association
EM End of Medium
EMI Electromagnetic Interface
ENQ ENQIRY
EOA End of Address
EOB End of Block
EOD End of Data
EOF End of File
EOJ End of Job
EOM End of Message
EOR End of Record
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EOT End of Text/Transmission
EPOS Electronic Point Of sale
EPROM Electrically Programmable Read-Only-Memory
EROM Erasable Read Only Memory
EUL End User License
EIDE Enhanced Integrated Drive Electronics
ENIAC Electronic Numeric Integrator and Calculator
EDAC Error Detection and Correction
ESC Escape Character Code
ESDI Enhanced Small Device Interface
EXNOR Exclusive Nor
EXOR Exclusive OR
EDVAC Electronic Discrete Variable Automatic Computer
Ff
FAM Fast Access Memory
FD Full Duplex
FDC Floppy Disk Controller
FDX Full Duplex
FEDS Fixed and Exchangeable Disk Storage
FEP Front End Processor
FET Field Effect Transmitor
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FF Form Feed/Flip-Flop
FIFO First in First out
FLOP Floating Point Operation
FD Floppy Disk
FORTRAN Formula Translator
FOSDISC Film Optical Scanning Device for Input into Computer
FROM Fusible Read Only Memory
FPD Flat Panel Display
FTP File Transfer Protocol
Gg
GINO Graphical Input Output
GKS Graphics Kernel System
GND Ground
GPIB General Purpose Interface Bus
GPR General Purpose Register
GPL General Public License
GB Giga Byte
GHZ Giga Hertz
GPS Geographical Positioning System
GUI Graphical User Interface
GIS Geographical Information System
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GPD Gas Plasma Display
Hh
H&Y Hype nation and Justification
HD Half Duplex
HDLIC High Data Link Control
HDX Half Duplex
HLDLIC High-Level Data Link Control
HLL High Level Language
HMI Human Machine Interface
HOF Head of Form
HRG High Resolution Graphics
Hz Hertz
HDTV High Definition Television
HF High Frequency
HTML Hyper Text Markup Language
HPNA Home Phone Line Network Adapter
Ii
IAM Intermediate Access Memory
IAR Instruction Address Register
IAS Intermediate Access Store
IBG Interblock Gap
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IC Integrated Circuit
ID Identification
IDP Integrated Data Processing
IEE Institution of Electrical Engineers
IEEE Instruction of Electrical and Electronic Engineers
IH Interrupt Handler
IKBS Intelligence Knowledge Based System
I/O Input/output
IOP Input/output Processor
IORQ Input/output Request
IP Information Provider
IPL Initial Program Leader
IPS Inches per Second
IPSE Integrated Project Support Environment
IR Information Retrieval
ISAM Indexed Sequential Access Method
ISDN Integrated Services Digital Network
ISO International Standards Organization
ISO/OSI International Standards Organizations/Open System Interconnection
ISR Information Storage and Retrieval
IT Information Technology
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ITS Invitation to Send
ICU Intensive Care Unit
IDE Integrated Drive Electronic
IrDA Infrared Data Association
IRQ Interrupt Request
IP Internet Protocol
ISA Industry Standard Architecture
IRC Internet Relay Chart
ISP Internet Service Provider
IMAP Internet Mail Access Protocol
ICT Information Communication Technology
IPX Inter-network Packet Exchange
IR Instruction Register
IBM International Business Machine
IRG Inter-Record Cap
Jj
JCL Job Control Language
JPEG Joint Photographic Experts Group
Kk
KB Kilo Byte
KIPS Kilo Instruction per Second
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KSR Keyboard Send/Receive
KW Kilo Word
KHz Kilo Hertz
KBps Kilobytes per Second
Ll
LAN Local Area Network
LASER Light Amplification by Stimulated Emission of Radiation
LSI Large Scale Integration
LIFO Last in First out
LCD Liquid Crystal Display
LCP Link Control Procedure
LSD List Significant Digit
LSB Least Significant Bit
LF Line Feed
LPM Lines per Minute
LIPS Logical Inferences per second
LISP List Processing
LLL Low-Level Language
LQ Letter Quality
LUT Look Up Table
LARC Liver more Automatic Research Computer
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LED Light Emitting Diodes
LPT Line Printer
Mm
MROM Mask Read Only Memory
Mbps Megabits per second
MFLOPS Mega Floating Point Operations per Second
MAC Message Authentication/medium Access Control
MAR Memory Address Register
MB Mega Byte
MBR Memory Buffer Register
MCP Master Control Program
MDR Memory Data Register
MICR Magnetic Ink Character Recognition
MIMD Multiple Instruction Stream Multiple Data
MIPS Million Instructions per Second
MIS Management Information System
MISD Multiple Instruction Stream-Single Data
MMI Man Machine Interface
MOS Metal Oxide Semi-conductor
MAN Metropolitan Area Network
MIC Magnetic Ink Character
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MSR Magnetic Strip Recognition
MODEM Modulator/Demodulator
MOSFET Metal Oxide Semi-conductor Field Effect Transistor
MPS Microprocessor System
MPU Microprocessor Unit
MSB Most Significant Bit
MSD Most Significant Digit
MSI Medium Scale Integration
MTBF Mean Time between Failures
MTF Mean Time to Fail
MUX Multiplexer
MM Memory Management
Nn
NAK Negative Acknowledgement
NCBD Natural Binary Coded Decimal
NC Numerical Control
NDR Non Destructive Readout
NEQ Non-Equivalence
NLQ Near Letter Quality
NMI Non-maskable Interrupt
NRZ Non-Return to Zero
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NCSA National Centre for Super Computing Applications
NCP Network Control Protocol
NLSP Network Link Services Protocol
NIC Network Interface Card
NDT Non-Destructive Testing
Oo
OA Office Automation
OCP Order Code Processor
OCR Optical Character Reader
OCR Optical Character Recognition
OEM Original Equipment Manufacture
OMR Optical Mark Reader
OMR Optical Mark Recognition
OS Operating System
OSI Open System Interconnection
O/P Output
OV Overflow
OBR Optical Bar Recognition
OC Optical card
OT Optical Tape
OOPL Object Oriented Programming Language
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Pp
PAD Packet Assembler Disassembler
PC Personal computer
PCB Printed Circuit Board
PCM Plug-compatible Manufacturer
PCU Peripheral Control Unit
PDL Page Description Language
PDL Program Design Language
PDN Public Data Network
PERT Program Evaluation and Review Technique
PIA Peripheral Interface Adapter
PID Personal Identification Device
PIN Personal Identification Number
PIO Parallel Input Output
PIPO Parallel Input/Parallel Output
PISO Parallel Input/Serial Output
PL Programming Language
PLA Programming Logic Array
PLD Programmable Logic Device
PL/M Programming Language for Microprocessors
PMOS P-channel Metal Oxide Semiconductor
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POL Problem Oriented Language
POS Point of Scale
PPM Pages per Minute
PROLOG Programming in Logic
PROM Programmable Read Only Memory
PS Pico Second
PSN Packed Switched Network
PSU Power Supply Unit
PSW Processor Status Word
PTR Paper Tape Reader
PCs Punched Cards
PDP Personal Digital Assistant
POST Power on Self Test
Ps/21 Personal System 2 Interface
POP Post Office Protocol
PPP Point to Point Protocol
PCMCIA Personal Computer Memory Card International Association
PCI Peripheral Components Interconnection
QBE Query by Example
QISAM Queved Indexed Sequential Access Method
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QSAM Queved Sequential Access Method
QL Query Language
Rr
R&D Research and Development
RAM Random Access Memory
RGB Red Green Blue
RISC Reduced Instruction Set Computer
RJE Remote Job Entry
RO Receive Only
ROM Read Only Memory
RPG Report Program Generator
RTE Real Time Execution
RTS Request to Send Signal
R/W Read/Write
R/WH Read/Write Head
RSI Repetitive Strain Injuries
RFC Request for Comments
RS Record Separator
Ss
SVGA Super Video Graphics Array
SAM Serial Access Memory
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SAR Store Address Register
SBC Single Board Computer
SCR Sequence Control Register
SCSI Small Computer System Interface
SD Single Density/Disk
SDLC Synchronous Data Link Control
SIMD Single Instruction Stream Multiple Data Stream
SIO Serial Input Output
SIPO Serial Input/Parallel Output
SISD Single Instruction Steam Single Data Stream
SISO Serial Input Serial Output
SLSI Super Language Scale Integration
SNA Systems Network Architecture
SNOBOL String Oriented Symbolic Language
SP Stack Pointer
SPX Simplex
SQA Software Quality Assurance
SSD Single Sided Disk
SSI Single Scale Integration
STX Start of Text
SD Super Disk
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SRAM Static Random Access Memory
SXGA Super Extended Graphics Array
SATA Serial Advanced Technology Attachment
STP Shielded Twisted Pair
SPX Sequence Packet Exchange
SMS Short Message Service
SMTP Simple Mail Transfer Protocol
SLIP Service Line Internet Protocol
Tt
TAB Tabulate
TAT Turn around Time
TDS Transaction Driven System
TTY Teletype
TV Television
TP Teleprocessing
TPI Tracks per Inch
TSW Telesoftware
TTL Transistor-Transistor Logic
TX Transmitter
TFTs Thin Film Transistors
TB Tera Byte
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TCP/IP Transmission Control Protocol
TCP Transmission Control Protocol
TELNET Terminal Emulation Protocol
TLD Top-Level-Domain
Uu
UART Universal Asynchronous Receiver Transmitter
UBC Universal Block Channel
ULA Uncommitted Logic Array
UPC Universal Product Code
UPS Uninterruptable Power Supply
USART Universal Synchronous Asynchronous Receiver Transmitter
USASCII Universal synchronous Asynchronous Standard for Information Interchange
USRT Universal synchronous Receiver Transmitter
UV Ultraviolet Light
UXGA Ultra Extended Graphics Array
USB Universal Serial Bus
UTP Unshielded Twisted Pair
UHF Ultra High Frequency
URL Uniform Resource Locator
UDP User Datagram Protocol
UTL Uganda Telecom Limited
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Vv
V&V Verification and Validation
VDT Visual Display Terminal
VDU Visual Display Unit
VFU Vertical Format Unit
VHD Very High Density
VLSI Very Large Integrated Circuits
VRAM Video Random Access Memory
VROM Video Read Only Memory
VRC Vertical Redundancy Checks
VS Virtual Storage
VGA Video Graphics Array
VCD Video Compact Disk
VR Virtual Reality
VSAT Very Small Aperture Terminal
VHF Very High Frequency
Ww
WAN Wide Area Network
WYSIWYG What You See Is What You Get
WYSIAYG What You See Is All You Get
WIMP Windows Icon Mouse Printers
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WISC Writable Instruction Set Computer
WORM Write Once Read Many
WP Word Processing
WPM Words per Minute
WOS Windows Operating System
WAP Wireless Application Protocol
WWW World Wide Web
Xx
XGA Extended Graphics Array
XHTML Extensible Hyper Text Markup Language
XML Extensible Markup Language
Zz
ZIF Zero Insertion Force
COMPUTER TERMS
AAL (ATM Adaptation Layer): adapts PDUs passed down from higher layers onto ATM cells
Active hub: allows multiple devices to be wired to a central location to share the same media and
regenerate the signal; also referred to as multiport repeaters.
ADSL (Asymmetric Digital Subscriber Line): typical form of xDSL telephone companies offer
to residences
AGP (accelerated or advanced graphics port): a high-speed, point-to-point channel for attaching
a graphics card to a computer’s motherboard, primarily to assist in the acceleration of 3D
computer graphics
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ALU (arithmetic logic unit): a digital circuit that calculates an arithmetic operation (e.g.,
addition, subtraction) and logic operations between two numbers; the fundamental building block
of the Central Processing Unit (CPU) or a computer
AM (amplitude modulation): a technique used for transmitting information via a radio carrier
wave
Amplitude: height of the wave at any point in the wave
ANSI (American National Standards Institute): a voluntary organization that coordinates the
development and use of consensus standards in the United States and represents the needs and
views of U.S. stakeholders in standardization forums around the globe
API (application programming interface): gives programmers a formal set of routines to call on
to use underlying network services
Application layer: performs the functions of file transfer, e-mail, etc. (see OSI Model)
Architecture: how a system is designed; includes how the components are connected to and
operate with each other
ARP (address resolution protocol): network layer protocol provided with TCP/IP; used to map
an IP (internet protocol) address to a MAC (media access card) address
ASCII (American Standard Code for Information Interchange): relates a number from 0 to 255
in the binary (base 2) form to keyboard characters
ASIC (application-specific integrated circuit): an integrated circuit designed for a particular use
(e.g., a chip designed solely to run a cell phone)
Asynchronous communication: describes when devices, such as computers, rely on their own
internal clocks; it provides connectivity to printers, modems, fax machines, etc.
ATM (asynchronous transfer mode): high bandwidth, cell-switching technology; designed to
carry many different types of information, including voice, video, image, data, and graphics;
another form of STDM (statistical time division multiplexing)
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AUI (attachment unit interface): a 15-pin connection that provides a path between a node’s
Ethernet interface and the medium attachment unit (MAU); also known as a transceiver
AS (Autonomous system): collection of IP networks under the control of a single entity
B (bearer) channel: carries voice, video, image, or data traffic, depending upon the equipment
and applications available
Bandwidth: expressed in a range of frequencies using hertz as the unit of measurement; also
called analog capacity
Base 2 System: binary number system, only two discrete values (0 and 1) are possible and all
numbers are a combination of these two characters; digital signals are numbers sent in the Base 2
system
Base 10 System: the decimal system
Baseband: describes signals and systems whose range of frequency is measured from 0 to a
maximum bandwidth or highest signal frequency; sometimes used as a noun for a band of
frequencies starting at 0
BGP (border gateway protocol): an inter autonomous system routing protocol; a network or
group of networks under a common administration and with common routing policies
Bit: contraction of the expression “binary digit”; smallest unit of data in a computer
BIOS (basic input/output system): the firmware code run by an IBM-compatible PC when first
powered on, known as “booting up”; primary function is to prepare the machine so other
software programs can load, execute, and assume control of the PC
Bluetooth: specification that allows mobile phones, computers, and PDAs to be connected
wirelessly over short ranges
Bps: bits per second: common measure of data speed for computer modems and transmission
carriers
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BRI (basic rate interface): an integrated services digital network configuration, usually intended
for the home and small enterprise (see also PRI)
Bricks and clicks: business that existed pre-Internet that now uses e-commerce technology to
sell on the Internet
Bridge: interprets the LAN hardware adapter address contained in MAC and decide whether to
filter or forward the frame; does not change the frame in any way
Browsers: client applications that access WWW servers
Building backbone: connects LANs within a building
Bus: electrical connection between any two components in a computer
Bus topology: system layout where electrical signals generated by a device connected anywhere
on the bus are received by all other connected devices
Byte: the standard size of data in a computer; 8-bits
Cache: keeps data the processor is likely to need quickly close at hand; increases processor
operation speed
CAD/CAM (computer-aided design/computer-aided MANUFACTURING ): software used to
design products such as electronic circuit boards in computers
Campus backbone: connects building LANs together
CD-R (compact disc - recordable): special type of CD-ROM that can be written onto by any
computer with a recording drive; can only be written onto once
CD-ROM (compact disc read-only memory): optical storage device read by lasers; can hold up
to 700 megabytes of data
CD-RW (compact disc - rewritable): special type of CD-ROM that can be written onto by any
computer with a recording drive; can be written onto more than once
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CIR (committed information rate): describes the user information transfer rate the network
supports during normal network operations
CLEC (competitive local exchange carrier): In the US, a telecommunications provider company
(also called a carrier) that competes with other, already established carriers (the local telephone
company)
Client/server architecture: network where some computers are dedicated clients (workstations)
and some are dedicated servers; information is centralized on the server, and an administrator
sets policies and manages it
CMOS (complementary metal-oxide semiconductor) RAM: requires very little power; maintains
information even when the computer is off
Collision: occurs when several network users communicate at the same time and interfere
(collide) with one another
Collision domain: logical network segment where data packets can "collide" with one another
for being sent on a shared medium, in particular in the Ethernet networking protocol
Computer networking: a combination of hardware and software that lets the various computers
in an organization communicate with one another
Computer operating system (OS): special computer program that provides an environment in
which other programs can use the computer’s central processor and the attached input/output
devices
Connectivity devices: bring users of the network into contact with one another
Constant bit rate (CBR): transmission that uses a set amount of network capacity on a
continual basis; used when the arrival of the information is time-sensitive
Convergence: the merging and sometimes clashing of voice and data
CPE (customer premises equipment): generally refers to telephones, DSL or cable modems, or
purchased set-top boxes for use with communication service providers’ services
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CPS (cycles per second): measure of how frequently an alternating current changes direction;
has been replaced by the term hertz (Hz)
CPU (Central Processing Unit): the brain of the computer system where calculations and
decisions are made; also referred to as the processor
CPU Speed: how fast the CPU works
CSU (channel service unit): provides a loopback function for telephone-company testing, and
checks bipolar signal generation
CRC (cyclic redundancy check): method of checking for errors in data that has been
transmitted on a communications link; a function used to produce a Checksum against a block of
data
CS (convergence sub-layer): particular protocols that are responsible for gathering and
formatting higher layer information so it can be processed by the lower layers
CSMA/CD (carrier sense multiple access/collision detect): set of rules for determining how
network devices response when two devices collide
D (data) channel: used for common channel signaling by both the telephone company switch
and the customer equipment; provides the call signals that set up B channel connections
DACS (digital access and cross-connect system): a piece of telecommunications equipment
used for routing T1 lines; can cross-connect any T1 line in the system with any other T1 line in
the system
Data: information manipulated inside the computer in the form of bits and bytes
Datagram: data packet that is sent over an IP network; associated with the network layer when
communication protocol is connectionless
DCE (data communications equipment OR data circuit-terminating equipment): a device that
communicates with a data terminal equipment (DTE) device in a particular standard
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DDP (datagram delivery protocol): a member of the AppleTalk networking protocol suite,
mainly responsible for socket-to-socket delivery of datagram over an AppleTalk network
DE (discard eligibility): signal used to identify less important data traffic that can be dropped
during periods of congestion on the system
DLCI (data link connection identifier): a channel number that tells the network how to route the
data
DMA (direct memory access): a feature that allows certain hardware subsystems in a computer
to access system memory for reading and/or writing independently of the CPU; can include disk
drive controllers, graphics cards, network cards, and sound cards
DOS (disk operating system): a family of closely related operating systems (COS) that ran on
IBM PC type hardware.
DNA (digital network architecture): a set of specifications or protocols created by Digital
Equipment Corporation (DECnet) that evolved into one of the first peer-to-peer network
architectures
DNS (domain name system): service that connects a domain name to an IP address
DRAM (dynamic random access memory): primary choice for holding large amounts of
information due to its inexpensive cost; must be refreshed or rewritten frequently (about every
386 milliseconds)
DS0 (digital signal, level 0): basic digital signaling rate of 64 kbit/s, corresponding to the
capacity of one voice-frequency-equivalent channel
DS1 (digital signal, level 1): also known as T1; widely used to transmit voice and data between
devices
DSL (digital subscriber line): technology that delivers digital data transmission over the wires of
a local telephone network
DVD (digital versatile disc): can hold over seven times as much information as CDs
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DWDM (dense wavelength-division multiplexing): an optical technology used to increase
bandwidth over existing fiber optic backbones (see building backbone, campus backbone)
EBCDIC (extended binary coded decimal interchange code): 8-bit character encoding table used
by ISM mainframes
EGP (exterior gateway protocol): a protocol commonly used between hosts on the Internet to
exchange routing table information
EMI (electromagnetic interference): radiation that causes unwanted signals (interference or
noise) to be induced in other circuits; also called radio frequency interference or RFI
Enterprise network: connects many types of networks
Ethernet: most commonly used protocol designed to change the packets into electrical signals
that can be sent out over the wire
Exterior protocols: routing protocol used between autonomous systems
FAT (file allocation table): table that the operating system uses to locate files on a disk; because
a file may be divided into many sections that are scattered around the disk, the FAT keeps track
of all the pieces
FDDI (fiber distributed data interface): a set of ANSI protocols for sending digital data over
fiber optic cable (see ANSI)
FDM (frequency-division multiplexing): permits a range of input signals to be carried over a
communication line that uses separate carrier frequencies for each signal channel; mostly used
for analog information but can carry digital
File management system: way to store and retrieve information from disk drives; controls how
files can be created, accessed, retrieved, and deleted
Firewall: a barrier between a network and the Internet through which only authorized users can
pass; set of security policies to screen incoming and outgoing messages; also used to isolate one
part of a network from another
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Floppy drive: early versions were actually floppy; today, they use hard 3.5 inch disk; also
referred to as removable drive
Frame: data structure that collectively represents the transmission stream (headers, data, and the
trailer) and provides the information necessary for the correct delivery of the data
Frame relay: service with standards and specifications designed to transmit data; some users
have had success at transmitting voice
FRAD (frame relay access device): software that frames the customer’s payload with the Frame
Relay overhead information, including the first DLCI (data link connection identifier) address, to
prepare it for delivery to the network
Frequency: number of times a wave repeats a cycle in a one-second period; measured in cycles
per second, or hertz
FTP (file transfer protocol): application used to transfer a copy of a file from one computer to
another computer with one acting as client and the other as server; a login with a user name and
password is typically required
Full-duplex link: enables both sides to simultaneously send and receive data; could require two
separate cables, one in each direction or a single multiplexed cable
Gateways: a node on a network that translates (converts protocol) from one operating system
environment to another
Gateway routers: used to implement exterior protocols and interconnect autonomous systems
Gbps (gigabits per second; billions of bits per second): a data transfer speed measurement for
high speed networks
GUI (graphical user interface): easy way of accessing applications with the use of a pointing
device, such as a mouse; pronounced “gooey”
Half-duplex link: enables one side to transmit and receive, but not simultaneously; information
only flows in one direction at a time using a control procedure to mediate
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Host-to-host layer: part of the TCP/IP model that performs the same function as the transport
layer in the OSI model
Host address: part of an IP address that is uniquely assigned by an administrator
HTTP (hypertext transfer protocol): protocol users interact with (by means of a browser) to
access Web pages over an internet or intranet
Hubs: bring the users of the network into contact with one another
Hz (hertz): unit of frequency; one hertz simply means one cycle per second, applied to any
periodic event (e.g., one tick of a clock is 1 Hz; the human heart beats at 1.2 Hz)
ILECs (incumbent local exchange carriers): a telephone company providing local service when
the Telecommunications Act of 1996 was enacted (see CLEC)
ILP (initial loader program): reads an existing file containing database records; also called a
boot-loader
Input/output management routines: provide orderly control and flow of information between a
computer’s main memory and attached peripheral devices
Interface: point in the system where the rules, control codes, formats, and information direction
(as dictated by the protocol) are implemented
Interior protocols: routing protocol used within/interior to an independent/ autonomous system
Internet layer: part of the TCP/IP model that performs the same function as the network layer of
the OSI model
Internetworking: connecting one network to another network
Interprocess communication: allows programs to share information dynamically, whether
running locally or remotely
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I/O (Input/output devices): hardware used to enter and retrieve data from the system
IP (internet protocol): network layer protocol provided with TCP/IP; connectionless, unreliable
protocol that provides features for addressing, type or service specification, fragmentation and
reassembly, and security
IP address (internet protocol address): logical address assigned to every workstation, server,
printer, and router on any interconnected network
IPX/SPX (Internetwork packets exchange/sequenced packet exchange): a networking
protocol used by the Novell NetWare operating systems; it is a datagram protocol used for
connectionless communications
IRC (Internet relay chat): allows groups to communicate interactively via keyboard and screen
display
ISDN (Integrated Services Digital Network): a circuit-switched telephone network system
designed to allow digital transmission of voice and data over ordinary copper telephone wires
ISDN PRI: switched-line service from telephone companies that operates over T1 (or E1/J1)
facilities
IS-IS (intermediate system-to-intermediate system): an interior gateway protocol (IGP) intended
for use within an administrative domain or network
ISPs (Internet service providers): businesses or organizations that provide consumers with access
to the Internet and related services
IT (information technology): broad term that can refer to anything from mainframes to PDAs;
any technology that moves information (voice, video, or data)
ITU-T (ITU Telecommunication Standardization Sector): coordinates standards for
telecommunications on behalf of the International Telecommunication Union (ITU)
IXC (interexchange carrier): a telephone company that provides connections between local
exchanges in different geographic areas
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Jitter: distortion in a digital signal caused by a shift in timing pulses; can cause data
interpretation errors
JPEG (Joint Photographic Experts Group): a lossy compression technique for color images;
pronounced jay-peg (see Lossy)
Kbps (thousands of bits per second): a measure of data transfer speed
kHz (kilohertz): a unit of measurement of frequency, also known as cycles per second; e.g., one
kilohertz equals 1,000 Hz, or cycles per second
LAN (local area network): network that operates within a small geographic area, usually within a
building, office, or department
LAPB (link access protocol, balanced): a data link protocol in the X.25 stack
LATAs (local access and transport areas): In the US, refers to a geographic region assigned to
one or more telephone companies for providing communication services
Layer 2 switches: interpret and make switching decisions on the LAN hardware adapter address
contained in the data link header of MAC frames; forward frames only to the destination
hardware address contained in the frame
LCI (logical channel identifier): used to define frequencies in use on M/A-COM EDACS
(Enhanced Digital Access Communications System) systems and LTR (logic trunked radio)
systems; more commonly known as logical channel number (see LCN); also known as virtual
channel
LCN (logical channel number): used to define frequencies in use on M/A-COM EDACS
(Enhanced Digital Access Communications System) systems and LTR (logic trunked radio)
systems; also known as the logical channel identifier (see LCI); also known as virtual channel
LE (local exchange): a regulatory term in telecommunications for local telephone company
Leased lines: another name for private lines, dedicated lines, or permanent circuits
LEC (local exchange carrier): a public telephone company in the US that provides local service
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LGN (logical channel group number): together with the LCN (in the X.25 packet header),
identifies the actual logical channel number of the DTE-DCE link; a 4-bit field representing a
number between 0 and 15
Line layer: layer of the OSI physical layer that is responsible for synchronizing and multiplexing
multiple streams of data into one SONET stream within SONET frames; also monitors and
administers SONET multiplexers
LLC (logical link control): standard interface allowing any combination of MAC techniques and
physical media to be used simultaneously in the same workstations; shields higher layer
protocols from the peculiarities of the physical medium
Logical segmentation devices: allow network designers to maintain separate networks (often for
security reasons) that can still communicate with one another
Lossy: data compression method where compressing and then decompressing retrieves data that
may well be different from the original, but is "close enough" to be useful in some way
LU (logical unit): identifies an end-user in IBM's Systems Network Architecture (SNA)
MAC (media access control) address: unique 6-byte address associated with and coded into each
network interface card (NIC); address assignment is controlled by the IEEE
MAN (metropolitan area network): connects sites in and around a large city
MB (megabyte): unit of information or computer storage equal to either exactly one million
bytes or, in some cases, 1,048,567 bytes, or more rarely, 1,024,000 bytes; not to be confused
with Mb, which stands for megabits
Mbps (megabits per second): a unit of information storage; not to be confused with MB or
megabytes
Medium: transmission, or system that carries the message or data
MAU (medium attachment unit): converts signals on an Ethernet cable to and from AUI signals
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Memory: desk space of the computer system; microchips located on the motherboard that hold
data and instructions for the CPU (central processing unit)
Memory management: allocates memory to separate tasks and protects data from corruption
Menu: used in some DOS shells and early versions of Windows; an improvement on the
command line but cumbersome when a task requires the submenu of a submenu of a submenu of
a menu item
Message: information content to be shared
MHz (megahertz): one hertz is one cycle per second; a megahertz is equal to one million cycles
per second
MIB (management information base): a type of database used to manage the devices in a
communications network
MPEG (Motion Picture Experts Group): digital video format identified by “.mpg” extension
after the file name; a working group of ISO/IEC charged with the development of video and
audio encoding standards; pronounced m-peg
MPLS (multiprotocol label switching): an initiative that integrates Layer 2 information about
network links (bandwidth, latency, utilization) into Layer 3 (IP) within a particular autonomous
system to simplify and improve IP packet exchange
Mpps (millions of packets per second): a measurement of information sent per second
Multiplexing: process of putting multiple signals on a wire simultaneously
Multiport repeaters: allow multiple devices to be wired to a central location, share the same
media, and regenerate (repeat) the signal; also referred to as active hubs
Multitasking routines: permit two or more distinct tasks to be performed concurrently by the
computer
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Name resolution: process by which the peer-to-peer name used on each conversational level is
related to other levels
NAP (network access point): transitional data communications facilities at which Network
Service Providers (NSPs) would exchange traffic, in replacement of the publicly-financed
NSFNet Internet backbone; now replaced by modern IXPs
NAT (network address translator): involves re-writing the source and/or destination addresses of
IP packets as they pass through a router or firewall; also called network masquerading, native
address translation, or IP-masquerading
NetBIOS (network basic input/output system): allows applications on separate computers to
communicate over a local area network (LAN)
Network access layer: allows a computer to exchange data with another computer over a
common network medium; part of the TCP/IP model that performs the same functions as the
data link and physical layers of the OSI model
Network address: part of an IP address that is uniquely assigned by one of the ICANN-
sanctioned agencies
Network design: how the various clients and servers are arranged for purposes of connectivity,
performance, and security
NOS (network operating system): optimizes the client/server architecture; provides and supports
network services such as file services, e-mail, Internet and intranet services, and applications
NIC (network interface card): hardware adapter that provides communication capabilities;
responsible for building, transmitting, receiving, and decoding frames in a LAN environment;
serves as the interface between the networked devices and the connecting wires
NNTP (network news transfer protocol): makes USENET possible; protocol for the distribution,
inquiry, retrieval, and posting of news articles using a reliable stream-based transmission of news
among the ARPAInternet community
Nonvolatile memory: chips that hold information even when the system is turned off
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NRZ-L (non-return to zero level): form of digital encoding; negative voltage is used to represent
a binary 1, and a positive voltage is used to represent a binary 0
NSP (network service provider): a business or organization that sells bandwidth or network
access by providing direct backbone access to the Internet, and usually access to it’s network
access points (see NAP)
OC1 (optical carrier, level 1): a fiber optic connection capable of transferring data at 51.85 Mbps
Operating environment: how the OS controls the hardware and application programs
OS (operating system): interface between the application (word processor, spreadsheet, etc.) and
the computer hardware
OSI (open systems interconnection) model: developed to provide a view of the distinct
functionalities that are required to implement each protocol layer; defines a complete range of
functions that can be achieved with data communications equipment
OSPF (open shortest path first): a link-state hierarchical interior gateway protocol (see IGP) for
network routing protocol.
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