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COMPUTER STUDIES

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[email protected], TEL;+256758-183719

COMPUTER STUDIES CURRICULUM SEQUENCE

SENIOR 1Term 1-2

Topic 1: Introduction to Computers

1.1 Computers Today 1.2 Evolution of Computers 1.3 Uses and Functions of a Computer 1.4 Computer Care and Safety 1.5 Keyboard and Navigation 1.6 Categories of Computers 1.7 Classification of Computers 1.8 The Computer System

Term 2-3 Topic 2: Computer Hardware 2.1 Components of Computer Hardware 2.2 Application of Hardware Components

SENIOR 2Term 1 Topic 3: Computer Software 3.1 Introduction to Software

3.2 System Software 3.3 Application Software

Term 2 Topic 4: Word processing 4.1 Introduction to Word Processing 4.2 Word Processing

Term 3 Topic 5: Computer Presentation 5.1 Introduction to Presentation Software 5.2 Presentations

SENIOR 3Term 1 Topic 6: System start up and configuration 6.1 Computer Booting

6.2 System Configuration 6.3 Software Installation 6.4 Computer Troubleshooting

Topic 7: Computer communication and Network

7.1 Introduction to Computer Communication 7.2 Computer Networks

Term 2 Topic 8: Spreadsheets 8.1 Introduction to Spreadsheets 8.2 Spreadsheets

Term 3 Topic 9: Web Designing 9.1 Introduction to Web Design 9.2 Web Design

SENIOR 4 Term 1 Topic 10: Databases 10.1 Introduction to Databases 10.2 Database Design

Term 2 Topic 11: Elementary Computer Programming

11.1 Introduction to Programming 11.2 Developing a Simple Program

Term 3 Topic 12: Trends in Computer 12.1 Computer Integrity and Security 12.2 Computer Ethics 12.3 Computers and Society 12.4 Emerging Technologies 12.5 Systems Analysis

Computer Studies

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12.6 Computer Professions

CONTENTS

Computer science...................................................................................................................................1

Why do we study computer?..................................................................................................................1

Tasks one can do with a computer.........................................................................................................1

Precautions that should be taken in a computer laboratory...................................................................2

The components of computer.................................................................................................................3

Characteristics of computers..................................................................................................................4

Uses of computers..................................................................................................................................6

Functions of computers..........................................................................................................................7

Advantages of computers.......................................................................................................................7

Disadvantages of computers..................................................................................................................8

Data and information.............................................................................................................................9

History of computers............................................................................................................................10

Evolution of computers........................................................................................................................10

Computer generations..........................................................................................................................11

Classification of computers..................................................................................................................14

Computer system.................................................................................................................................18

Computer hard ware.............................................................................................................................19

System unit...........................................................................................................................................19

Memory measurements........................................................................................................................23

Coding systems....................................................................................................................................24

Printers.................................................................................................................................................26

Input devices........................................................................................................................................28

Processing devices...............................................................................................................................31

Secondary storage devices...................................................................................................................32

Computer software...............................................................................................................................37

System software...................................................................................................................................38

Operating systems (os).........................................................................................................................39 Computer Studies

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Interfaces..............................................................................................................................................41

Application software............................................................................................................................43

Programming languages.......................................................................................................................45

Language processors............................................................................................................................47

Utilities.................................................................................................................................................48

Viruses.................................................................................................................................................49

Hacking................................................................................................................................................54

Computer errors...................................................................................................................................55

Theft and system crashes.....................................................................................................................55

Computer crimes..................................................................................................................................55

Downloading and uploading................................................................................................................56

Booting.................................................................................................................................................56

Computer networking..........................................................................................................................58

Network types......................................................................................................................................59

Categories of computer networks........................................................................................................60

Requirements for networking computers.............................................................................................61

Communication media.........................................................................................................................62

Cables...................................................................................................................................................62

Micro waves.........................................................................................................................................64

Satellites...............................................................................................................................................64

Infrared.................................................................................................................................................64

Network topologies..............................................................................................................................65

Advantages of networking...................................................................................................................66

Disadvantages of networking...............................................................................................................66

Network connection types....................................................................................................................67

Network security..................................................................................................................................67

Server security.....................................................................................................................................68

Firewall security...................................................................................................................................69

Network users......................................................................................................................................69

Computer maintenance........................................................................................................................69

Data security and control.....................................................................................................................70

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Computer security................................................................................................................................70

The internet..........................................................................................................................................72

History of the internet..........................................................................................................................73

Uses of the internet..............................................................................................................................74

Advantages of the internet...................................................................................................................74

Disadvantages of the internet...............................................................................................................75

Factors that affect communication over the internet............................................................................75

Requirements for an internet connection.............................................................................................76

Transmission media.............................................................................................................................76

Internet service provider (isp)..............................................................................................................77

The web and web browsers..................................................................................................................78

Protocols..............................................................................................................................................82

The e-mail............................................................................................................................................83

Facilities of e-mail...............................................................................................................................84

Uses of e-mail......................................................................................................................................84

Advantages of e-mail...........................................................................................................................84

Disadvantages of e-mail.......................................................................................................................85

Features of an e-mail window..............................................................................................................85

Information technology........................................................................................................................87

Future evolutions of computer systems...............................................................................................90

Impact of computers in our society today............................................................................................93

Career opportunities in the computer field 94

Computer Studies

SENIOR ONE TERM 1-2

COMPUTER SCIENCEComputer science is concerned with the application of scientific principals to the design, construction and maintenance of system based on the use of computers.

What is a computer?

1. A computer is an electric device that can accept data, process, store and output information.

2. It can also be referred to as an automatic digital machine that under the control of a program, inputs data, processes data, stores data, retrieves, and transmits information

3. A computer is an electric machine that performs tasks in response to fed/ stored instructions or programs.

A computer accepts data, processes data, stores data and outputs information.

The major functions of a computer are; inputting, processing, storing, and outputting information.

Why do we study computer?1. Studying computer help us to demonstrate general knowledge and skills in the use of computer

and related technology.

2. It helps to use the knowledge acquired in computer to enhance learning in other subjects

3. To acquire basic computer skills required for employment.

4. To acquire knowledge used as a foundation for further studies in computer science.

5. It helps us use a variety of computer technology to access, analyze, interpret, apply, and communicate information.

Tasks one can do with a computerWhen we ask ourselves why we use computers today, we come up with many answers. We can not even imagine what our world would be without computers!

The following are some of the things that can be done using a computer.

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E-mail communication

Word processing

Saving

Printing

Storing

Study guides

Manipulating data

Entertainment

Statistical analysis

Computer Handbook | [email protected]

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PRECAUTIONS THAT SHOULD BE TAKEN IN A COMPUTER LABORATORY1. Switch on the computer system starting from the wall socket, UPS or stabilizer,

computer then other peripherals like a printer.

2. Avoid making connections when the computer is on power e.g. keyboard connections, mouse, printer, monitor, e.t.c.

3. Avoid abrupt switching off and on of the computer system. Use the normal way of shutting or closing down all the programs then shut down the computer from the start button.

4. Place the microcomputer in a dust free environment with good ventilation. Dust covers should be used to cover the microcomputer when not in use and if you are using polythene covers then do not cover the computer immediately after switching off as it will trap heat.

5. The microcomputer should not be exposed to direct sunlight.

6. The computers should be regularly serviced at least once a year, or more frequently if the environment is dusty. The service should normally include blowing the dust from the system unit, cleaning the floppy drives, keyboard, including all the keyboard contacts, also clean the monitor externally and the computer equipment regularly with a wet cloth. Make sure you don’t drop water in the computer system. If water drops in accidentally do not use the computer immediately until water has completely evaporated.

7. Do not open the computer for inside cleaning, this should be handled by qualified personnel.

8. It is good practice to keep record of the daily condition in case of computer failure.

9. The peripheral devices such as printers and mouse should be regularly serviced.

10. The floppy disks used for installation of programs and backups should be kept safely in disk banks and kept away from sunlight and magnetic media.

11. Floppy diskettes have to be write-protected all the time especially for installation diskettes (using protection tabs) and remove the write protect when writing on the diskettes if they are used for backup.


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12. In areas where the power fluctuates, it is important to use either a stabilizer or Uninterruptible power supply (UPS) to ensure steady input of power to computer system.

13. Food and drinks should not be allowed near the computers

14. Avoid smoking from the computer room

15. The computer system should not be connected to an electric line shared by other heavy equipments

THE COMPONENTS OF COMPUTERA computer is made up of a collection of different components that are interconnected in order to function as a single unit. It is composed of a system unit and peripheral devices.

1. System unit.

The system unit is a box-like case that houses the electronic components of a computer used to process data. It is made of a metal or plastic and protects the internal electronic components like; mother board, hard disk, disk drives, memory board, etc.

This is the part that houses the brain of the computer called the central processing unit (CPU). It is sometimes called chassis.


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2. Peripheral devices

These are devices connected to the system unit using cables that transmit data and information to and from the devices. The cables are attached to the system unit through ports.

Key board.

This is the most common peripheral device which helps the user to input data or to enter data and instructions in a computer.

The mouse.

It is a pointing device that enables the user to execute commands and complements the keyboard and the monitor. Its basic task is to move the cursor or pointer to different positions on the screen/monitor.

The printer.

A printer is a computer peripheral device used to produce information on a piece of paper. It is a computerized machine used to produce a hard copy or print out.

Monitor

A monitor or simply a screen is a television-like structure that enables the user to see what is going on in the computer. It is one of the most important components of a computer system. It enables the user to have a visual display of any data in the computer.

CHARACTERISTICS OF COMPUTERS1. Automation; Computers work automatically, they work under least external

control. They do not need any super vision in order to perform programmed routines.

2. Artificial intelligence; Computers are artificially intelligent. They can respond to requests given to them and provide solutions. They are designed to follow instructions as they are issued.

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 e.g. robots, expert systems, natural language processing.


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3. Diligence; Computers have the ability to perform the same task over and over for long hours without getting bored. Therefore computing devices must be able to perform the same routines repeatedly e.g. robots in industries.

4. Speed; computers are quite fast in their operation. A computer is speedy, capable of accomplishing millions of instructions per second (any task within a short time).

5. Storage; Computers have an internal storage (memory) for storing both instructions and data, being processed

6. Computers comprise of electronic elements like transistors, resistors, and chips.

7. Computers use programs (set of instructions) which specify the procedure of operations to be followed.

8. Computers exist in varying sizes, speed of processing, memory capacity, use and cost.

USES OF COMPUTERSComputers are widely used in our everyday life to accomplish various tasks. Today computer use is as wide as the user can imagine. Some of the areas that computers are widely used today include:

1. Research

In this present generation, advancements in scientific research have been possible mainly due to use of computers. New drugs have been introduced, exploration into space is possible even where human beings cannot survive, machines with various computers are sent in space and data is transmitted back to earth.

2. Education purposes

With the development of the computer, the internet has emerged. People now are able to link up with big universities and libraries overseas hence facilitating education. This is called e-learning.

3. Recreation purposes/ entertainment/leisure

When bored in the office, you can just double click an icon on your computer and you play cards, golf or any other computer game.

4. Business


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Many businesses have benefited profits from the use of computers to carry out calculations, monitoring of the business and reduction of the banking sector. Computers do most of the work.

5. Telecommunication industry computers have helped the telecommunication industry to transform the whole world into a village.

6. Electronic money transfer

There is easy means of transferring money through electronic means world wide in a fraction of a second e.g. western union, money gram.

7. Automatic teller machines (ATM)

These are machines that act as artificial tellers in receiving and issuing cash to bank customers at any convenient time and place.

8. Banking services

All banking services have been computerized and thus made easy for bankers to access individual accounts.

9. Security and military

Computers and computerized equipment are applied to ensure security in banks, offices and homes like computerized sensors, electronic cameras and scanners which are used to capture data for security.

10. Medical field

Theatre equipments are computerized to ease the work of doctors while operating patients.

11. Weather forecast.

12. Industry/manufacturing

13. They can be used for doing professional work, such as preparing presentations or writing reports, memos, speeches and many others.

FUNCTIONS OF COMPUTERS1. To convert data into information the computer is very fast in processing data


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2. Store information, safer than the physical storage like box files and cabinets for future use.

3. For quick, effective and accurate retrieval of information.

4. In projections e.g. weather forecasting {predictions, sales, projection in a company}

ADVANTAGES OF COMPUTERS1. Flexible

A computer is a flexible machine that can perform a variety of jobs as long as they are programmed in its memory

2. Faster

A computer is the fastest processing machine, on the market. It can process a lot of work within a very short time. The speed of the computer allows it to perform billions of activities within short time.

3. Automatic

It is automatic in nature, once properly set and switched on, it can operate for a long time with least human interference.

4. Cheap in long run

It is cheap in the long run to buy a computer. The cost effectiveness is realized by the amount of space saved in an office, saving on paper, in the filling system, and saving on labor.

5. Accurate

The computer is the most accurate machine on the market today in performing any task given. If fed with the right data, it will always produce high quality work.

6. Reliable

It is a reliable machine that executes whatever it is instructed to do in the most appropriate way.


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7. Operate in dangerous areas

A computer operates in very dangerous conditions for human beings for example dangerous chemicals like in cement manufacture and nuclear plants.

8. The computer produces better information because its output is usually tidy, timely and error free.

9. It stores and retrieves huge volumes of data.

10. The computer performs huge volumes of data effectively.

11. It simplifies problems solving by using programs and formulas designed for the purpose.

12. It stores formulas

DISADVANTAGES OF COMPUTERS1. Computer failure or break down may lead to lose of information.

2. Computers are very expensive or costly. The initial cost of purchase and cost of maintenance of the computers are very high.

3. The computer technology is full of changes. The technology is moving very fast and there is no guarantee that already bought machines could not become obsolete (out of date) in the next month.

4. The computer system can be cheated by knowledgeable people to steal. (Conmen).

5. Computers cause health problems like eye effects, cancer, repetitive strain injury, e.t.c.

6. the computer cannot solve all problems cost effectively e.g. thinking

7. All records in the computer are kept in a form that is not visible.

8. A computer has no common sense and will always do what it is instructed to do no matter how wrong or right it would be.

9. Computers lead to unemployment.

10. The computer is delicate; it needs to be handled with a lot of care.

11. When attacked by the virus, all the data may be lost


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12. Computers do not protect individual privacy.

13. Computer addiction by young people e.g playing games and over surfing,

14. Moral problems through access to pornographic material on computers.

15. Widening the gap between the rich and the o=poor as the rich produce more and at a faster rate using robots flooding the markets.

DATA AND INFORMATION

DATA

These are the raw facts represented by numeric, alphabetic characters and special symbols that are processed into information by the computer e.g. names, age of students.

DATA PROCESSING

This consists of receiving data (input) and processing it according to prescribed rules with the intentions of producing information (output) and storing information for future reference

INFORMATION

This refers to processed data. Is that data which is organized into meaning full and useful facts. It is data that has been transformed into meaningful and useful information for specific operations in organizations.

INFORMATION PROCESSING

It involves all activities which are necessary to convert raw data into useful information to be used for decision making.

The full set of operations that take place from collection of input to the availability of output is referred to as the information processing cycle.

HISTORY OF COMPUTERSThe computing ideas started long ago in the great river valley of Egypt, East Asia and China. Beginning with the Abacus as the first computers, but computing was not so significant until the 1940s when the first electronic computers were produced.


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Before the digital computers came into existence, many computing tools were developed and used to do simple mathematical calculations and operations for example slide rules, calculators, abacus, Napier bones, watches and tables of logarithms.

These first computers had distinguishing features like;

1. Most of them were mechanical in nature, as time went on some of them were run by electrical motors and used punched cards.

2. These computers were very huge in size and occupied very large space.3. Their processing power was very low4. They could do a few tasks like adding and subtracting numbers.5. They used vacuum tubes which were so big, later they were replaced with

transistors and later by integrated circuits on silicon board.

Since the end of the Second World War, new generations of computers replaced the old forms. Each generation has been characterized by a reduction in size, improvement in technology and an increase in performance capabilities.

EVOLUTION OF COMPUTERSThis is the gradual development of computers in terms of technology and physical size.

Over the centuries people have developed amazing varieties of data processing tools and techniques. The following are some of the different machines that were developed over years by different people.

1. The abacus (5000 BC).

The abacus was a Chinese instrument (mechanical calculator) with moving parts which was used in arithmetic calculations. It has bead-like parts that move along rods and could not store data before the next operation was carried out.

2. Napier’s bones

This mathematical device was through efforts of Scotsman John Napier. He invented a set of multiplication tables or ivory sticks that could slide back and forth to indicate certain results. Napier’s bones was used to do division and multiplication.

3. Slide rule (1620)


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It was introduced for the solution of widely applicable engineering formulas or for business calculations such as determination of simple interest, interest accumulation and depreciation. The slide rule was invented by the English mathematician William Oughtred, he also invented the logarithms.

4. Mechanical computer (1623-1940s)

These were characterized with mechanical gears moving parts i.e. wheels and axles and they used punched cards as means of storage.

Electromechanical computers were electronic and had movable parts.

5. Pascal's calculator.

A French mathematician and philosopher Blaise Pascal invented the 1st mechanical digital calculator that could perform addition and subtraction.

The calculator was called the Pascaline. The calculator was later improved by Leibniz to perform additional multiplication and division.

6. Babbage's engine (1822)

Charles Babbage an English man invented an engine for calculation of arithmetic programs in the machine. He called the first machine the difference engine. It was designed to compute and print tables of polynomials by repeated addition of differences.

7. Valdeniar Paulson (1900) discovered the magnetic storage media principles e.g. magnetic tapes.

COMPUTER GENERATIONSIt refers to the state of improvement in the development and advancement of computer technology which has been classified into four generations.

Each generation is characterized by significant improvements over;

Technology used to build the computer; Internal organization and operation of the computer; Programming languages

FIRST GENERATION (1946 - 1958)

These machines were basically used in the processing of payrolls as well as billing. Examples of these machines included IBM 650 and UNIVAC1.


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Key Characteristics

They were huge, expensive and often broke down They used vacuum tubes to control internal operations Used punched cards for input and output Used magnetic drums for primary memory. Had limited primary memory Their internal storage capacity was limited They were slow compared to today’s’ computers They required human operators to set switches They consumed a lot of power, generated a lot of heat and maintenance costs

were high. Programming was done in machine and assembler languages

SECOND GENERATION (1959 - 1964)

In 1947 three scientists, John Bardeen, William Shockley, and Walter Britain working at AT&T's Bell Labs invented what would replace the vacuum tube forever. This invention was the transistor which functions like a vacuum tube in that it can be used to relay and switch electronic signals.

This generation marked the introduction of super computer e.g. Livermore Atomic Research Computer (LARC) and the IBM 7030. Others were IBM 1401, Honeywell 200, CDC 1604 etc.

Key Characteristics

Used transistors for their internal operations They used magnetic card as a primary internal storage medium Increased storage capacity compared to first generation They had great reduction in size and heat generation Increased speed and reliability compared to first generation Programming was done using high level languages such as FORTRAN and

COBOL.

THE THIRD GENERATION (1964-72)

Integrated circuits (I.Cs) were a tremendous breakthrough in advancing of the computer. The integrated circuit, or as it is sometimes referred to as semiconductor chip, packs a huge number of circuits onto a single wafer of silicon. Robert Noyce and Jack Kilby independently discovered the amazing attributes of integrated circuits.


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They consisted of fast mainframe computers such as IBM360, IBM370, PDP-11 and 8-bit microcomputers.

Key Characteristics

Integrated circuits (IC) were introduced for internal operations. The computers reduced in size, price and become more reliable, faster and of

higher capacity. Introduction of operating system e.g. Multics. Development of microprocessors. (8008, 80286, 80386) Keyboards and Monitors for input and output. Magnetic disk was developed for storage purposes. The use of computer chips started in this period. It marked the introduction of personal computers. Introduction of simple programming language, e.g. Basic.

FOURTH GENERATION (1973 and above)

This generation can be characterized by both the jump to monolithic integrated.

Ted Hoff, employed by Intel (Robert Noyce's new company) invented a chip the size of a pencil eraser that could do all the computing and logic work of a computer. . Examples include the Altair 8800 computer kit, the Apple II and in 1981 IBM entered the PC market.

Key Characteristics

Introduction of wider varieties of software e.g. word processing, spread sheets, database management programs etc.

Large scale integration circuits (L.S.I) and very large-scale integrated circuits (V.L.S.I) were developed that contained hundreds to millions of transistors on tiny chip.

Non impact printers were developed for output purposes; they were faster and produced better quality prints.

Computers became more powerful and cheap, that schools and homes were able to purchase them.

Micro computers were developed with increased storage, considerably faster and smaller in size.

Use SDRAM chips for primary memory


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There was change in computer size, appearance, costs, availability and capability, and the computer’s main memory capacity increased and their cost decreased

FIFTH GENERATION

In the fifth generation, artificial intelligence computers which simulate aspects of human thought is likely to be developed and applied in programming language. They will use artificial intelligence systems that accept to achieve human like qualities of intelligence including the ability to reason.

It will lead to the development of supper computer that is faster and more powerful than others.

It will be based on logical inference operations. It is aimed at narrowing the gap between human beings and the preset day

computers.

CLASSIFICATION OF COMPUTERSComputers can be classified according to size, function, purpose, or processor power.

CLASSIFICATION BY SIZE

Computers can be classified depending on the user capacity and size of the machine. These include;

Super computers. Main frame Mini frame Micro computers

SUPER COMPUTERS

These are the largest, fastest, most expensive and powerful computers available. These carry out complex scientific applications like weather forecasting which require a large amount of data to be manipulated. They have multiple processors and superior technology that require a lot of computational power. With multiple processors a single task is split among processors for faster execution. All these processors are controlled by a single central processor e.g. CRAY T3D and NEC-500.

They are also called MONSTER computers.

The processing power of these machines is very high.


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They are owned by large scale organizations, they are not owned by individuals.

They are used for weather forecasting, nuclear weapons development and energy supply and conservation.

MAIN FRAME COMPUTERS

These are large general computers with extensive processing speed, storage and input/output capabilities. Main frames can process large amounts of data very quickly and are therefore used by big companies, banks and government departments. They can handle between 500-1000 users at the same time and have enormous backing storage capacity e.g. IBM 4381, ICL 39 series and the CDC Cyber series.

They are found in large and busy organizations, they are very expensive and they have high processing speed.

MINI FRAME COMPUTERS

These are physically smaller computers compared to the main frame. They support a number of concurrent users, but are usually slower than main frame computers. They have the same structures as the main frame and support the same peripheral devices but can only be connected to between 50-500 users. They are used in business and commerce and can be used for applications such as payroll, invoicing and stock control.

They are used for special purposes. They are slightly cheaper than the main frame. They are very fast as main frame computers.

MICRO COMPUTERS

These are smaller in size compared to the main frame and the mini frame computers. The “brain” of the micro computer is the micro processor. Computers fit on the desktop and the low cost of micro processors led to the development of laptops, notebooks, palmtops and desktop computers.

They are in form of personal computers (PCs). They are relatively faster compared to the above. They are used in homes, schools, offices, etc.

The examples include; desktop computers, laptop, palmtop computers (PDA).

Desktop computers


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These are designed to be stationed in one place probably on top of a desk. They can be put either at home or in the office. They are standard PC’s and development of other computers has evolved around these ones.

Laptop computers

These are designed for mobile computing. They have all facilities and system resources offered by desktop computers. Earlier laptops hard fewer resources like hard disks but modern ones have better resources than most desktops.

Personal Digital Assistants (PDA’s)

These are hand held devices which do not emulate all the features of a desktop. They are designed for people who are ever on the move. They easily fit in a shirt pocket and at any time one can check for e-mails, take a few notes, e.t.c. modern PDA’s have been integrated within cellular phones.

CLASSIFICATION BY PROCESS

These computers are classified according to how the data processed is presented. They include; Digital, analog and hybrid computers.

DIGITAL COMPUTERS

These are computers that process data that is represented in the form of discrete values. Discrete values are numbers that can be defined like 1, 2, 3, e.t.c. Digital watches are the best example; they have special tiny digital computers within them. The accuracy of digital computers depends on the memory size and the precision of the data input.

CHARACTERISTICS OF DIGITAL COMPUTERS

They have a high speed of processing data. They compare values and store results. They recognize data by counting discrete signals, representing either 1 or 0.Digital computers can be divided into general and dedicated computers.

ANALOG COMPUTERS

These are computers that perform arithmetic and logic operations in a continuous form by measuring physical changes like temperature, pressure, e.t.c.


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CHARACTERISTICS OF ANALOG COMPUTERS

They are attached to measuring instruments such as thermometers and voltmeters.

They process data in form of electrical voltages. The output from analog is often in the form of smooth graphs from which

information can be read. It measures values of continuously variables.

The best example; thermometer, voltmeter anemometer,

Differences between digital and analog computers

Digital computers Analog computers

Process data in discrete form Process data in continuous form

Not continuous (discrete) voltage Continuous voltage

Can only have one or two voltage levels Can have any voltage

Voltage jumps between levels Wavy voltage as time progresses

HYBRID

These are computers with combined features of digital and analog computers. These are the modern day computers.

CLASSIFICATION BY PURPOSE

These computers are classified according to the work they are designed for. These are classified into;

Special purpose. General purpose. Dedicated

SPECIAL PURPOSE

These are computers that perform specific tasks. They are designed to handle only a particular job, task, or to solve problems of a restricted nature for example; digital watches, calculators, computers in petrol pumps and in weapons like missiles, lifts in tall building etc.

GENERAL PURPOSE


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These are computers that are designed to solve a wide variety of problems. They are adopted to perform a variety of tasks by means of specifically written instructions. General purpose computers can perform calculations, keep date and time, word process documents, store data etc. e.g. personal computers.

DEDICATED COMPUTERSThese are general computers dedicated to specific purposes. They are committed to some processing task, though capable of a variety of tasks. A general purpose computer, for example can be dedicated to carrying out word processing tasks only.

CLASSIFICATION BY PROCESSOR POWER

These computers are classified according to the speed (power) with which they process data. The higher the processing power, the faster the computer is. Earlier computers had a processing power of less than 0.4 MIPS, (millions of instructions per second) but today, 15 MIPS is the minimum. Computers with high processing power also require more system resources, these resources include; system memory, hard disk space, and modern programs. The most common types of processor power are. 80286, 80386, 80486, Pentium I, Pentium II, Pentium III, Pentium IV, Intel Celeron, e.t.c

COMPUTER SYSTEMComputer system refers to the functional unit of a computer, which must be available for the computer to perform tasks. This consists of input units, processing unit, memory storage and output unit.

A computer system is basically comprised of three parts.

1. Computer hardware

2. Computer software

3. Trained personnel/live ware.

COMPUTER SYSTEM

HARDWARESOFTWARE LIVEWARE


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OUTPUT INPUT APPLICATION SYSTEM

DEVICES DEVICES SOFTWARE SOFTWARE

PERIPHERALS SYSTEM UNIT PROGRAMMING LANGUAGES

A typical computer system consists of several parts;

Computer case (system unit) that contains all the major components of computer processing unit

Monitor, which displays text and images Keyboard, that allows the user to type information and instructions into the

computer Mouse; that helps the user to select and move items on the screen. Printer, that produces a paper copy(hard copy) of the document created Modem, that allows computers communicate through telephone lines.

TRAINED PERSONNEL

Is at times known as live ware, this is the person who can operate a computer. Live ware is also divided into two;

1. The expert; the professional who operates the computer.

2. The end user

SENIOR ONE TERM 2-3

COMPUTER HARD WAREComputer hardware refers to the electronic, electric and mechanical components that make up a computer OR the physically seen and tangible parts of the computer used


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in processing data and delivering information. Hardware consists of all the machinery and equipment in a computer.

The computer hardware is divided into;


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System unit Input devices Out put devices Storage devices


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However the major examples of computer hardware are; Monitor, keyboard, Mouse, System unit, Printer, Plotter, Modem e.t.c.

SYSTEM UNIT

This is the most important component of the computer, and is at times referred to as subsystem. It is a box-like case that houses the electronic components of a computer used to process data.

It protects the internal electronic components from damage.

The system unit houses the following; mother board, Processor chip (CPU), data buses, hard disk, RAM chips, ROM chips, PC (PCMCIA) slots and cards, ports, disk drives, power supply, etc.

CENTRAL PROCESSING UNIT (C.P.U.)

This handles all the processing of information that takes place in the computer.

The CPU contains;

Control unit (CU)This controls the entire operation of the microprocessor during the execution of a program i.e. it carries messages to and from the main memory. It directs and coordinates most of the operations in the computer. For every instruction, the control unit repeats a set of four basic operations called the machine cycle or instruction cycle. It extracts instructions from the main memory, decodes them and executes them.

Decoding is the process of translating the instructions into commands the computer can execute.

Executing instructions is the process of carrying out the commands.It tells the rest of the computer how to carry out a program’s instructions.

The arithmetic and logical unit (ALU) This performs the execution part of a machine. It handles the arithmetic operations, logical operations and controls the speed of the operations. It specifically performs arithmetic, comparison and logical operations.Arithmetic operations include addition, multiplication and division.Comparison operations involve comparing one data item to another and determine if the first term is greater or equal to or less than the other. Logical operations work with conditions and logical operators such as AND, OR and NOT.


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Main memoryAlso known as memory, primary storage, internal memory or random access memory (RAM), refers to working storage. It acts as space where programs and data are kept during operation. Data stored in memory is represented as electrical voltages which are either on or off. The contents of main memory are temporal i.e. if the computer is turned off before saving work, the latest edits are lost.It is characterized by fast access to information, low capacity and high costs.Main memory carries out the following; Holds data for processing. Holds instructions for processing the data. Holds processed data waiting to be sent to an output or secondary storage device.

Computer storage is divided into two main parts:

PRIMARY STORAGE

This is temporally memory. It is fast because it is accessed electronically and no mechanical components are involved e.g. RAM, ROM, EPROM, EEPROM, VIRTUAL MEMORY, CACHE MEMORY, dynamic RAM, RAM BUS DRAM, Synchronous DRAM, static RAM, Registers.

Most memory (except ROM, flash memory and CMOS) is volatile i.e. its contents are lost when electric current is turned off and contents must be transferred to backing storage before the computer is turned off.

This memory is expensive and its storage size on a computer is usually limited when compared with backing storage.

SECONDARY STORAGE

This is also called backing storage. It is nonvolatile and contents stored are relatively more permanent when compared with memory. e.g. hard disk,, flash disk, floppy disk, CD, DVD, VCD, magnetic tapes.

Backing storage provides a cheap and almost an unlimited amount of storage. It is slow because of the mechanical components involved.

Major differences between primary and secondary storage

PRIMARY STORAGE SECONDARY STORAGE Located within the CPU Lower capacity

Located outside the CPU Higher capacity


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Faster access time Volatile Data can be processed from directly from storage More expensive Data can be processed.

Slow access time Non volatile Data cannot be processed directly but must be moved into main memory Less expensive Data can not be processed directly.

READ ONLY MEMORY (ROM)

This memory contains the permanently stored programs and data, which are placed in the computer by the manufacture. It cannot be altered or erased/deleted from the computer. It is non-volatile, read only, permanent and normally non increasable.

It is used to store software and configurations used in booting a computer.

ADVANTAGES OF ROM

it has a high bit density

its none volatile

it is cheap

DISADVANTAGES OF ROM

it takes long during the production process

it can not be changed

PROGRAMMABLE READ ONLY MEMORY (PROM)

PROM is read only memory that can be programmed directly by the user using a special PROM programmer. They come blank having nothing programmed but once programmed and the instructions stored in memory, it can not be changed. This is common with compact disk recordable (CD-R).

ERASABLE READ ONLY MEMORY (EPROM)

This is read only memory in which instructions can only be erased once and then reprogrammed. After, the instructions can not be changed e.g. compact disk re-writable (CD-RW)

ELECTRONICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY (EEPROM)


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This memory enables a user to put instructions in this memory as many times as one may wish until when one may wish to alter the instruction. The instructions remain in memory unchanged until one wishes otherwise e.g. colored TV use this memory. One can always program various TV channels at one time and then reprogram them to other channels at another time.

ELECTRONICALLY ALTERABLE READ ONLY MEMORY (EAROM)

This is ROM that can be read from and written to. However, since the two processes are significantly different, the EAROM can be called a read-mostly memory. Writing to takes more time compared to reading from thus the EAROM can not be used as a general purpose read/write memory. It is applied in limited critical industrial and military applications. Its non-volatile and does not require an auxiliary power source.

RANDOM ACCESS MEMORY (RAM)

This is the working memory, where programs and data are stored temporarily, while the computer is turned on. Every computer comes with RAM. It is volatile, read and write, temporally and it can also be increased.

RAM is the primary storage device that holds:

data that is input from the keyboard Data and programs read from secondary storage devices e.g. floppy disks, flash

disks, Compact Disks etc. Results after processing from the central processing unit.

FUNCTIONS OF RAM

To store a copy of the main software program that controls the general operation of computers

Temporary storage of a copy of an application program for interpretation and execution by the CPU.

Temporary storage of data items that have been input from the key board or other input devices.

Temporary storage of information that has been produced as a result of processing from the CPU

DIFFERENCES BETWEEN RAM AND ROM

RAM ROM


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Is volatile Is non volatile

Is read and write Is read only

Is temporally Is permanent

Can be increased Is normally not increased

VIRTUAL MEMORY

It is used in case the main memory is not enough. It is used for emergency when the main memory is not enough; therefore part of the programs will be stored in the main memory and another part in the virtual memory.

CACHE MEMORY

It helps the main memory (RAM) to be faster. It transfers information from primary to secondary memory. It helps in improving memory transparency thus raising the processor speed. It also provides space for temporary storage of frequently accessed data.

MEMORY MEASUREMENTS

All computers work on a binary numbering system i.e. they process data in one’s or zero’s. Data is represented electronically by storage cells which are either charged or discharged. The computer system is made up of logic that works only with two states “ON” and “OFF”. The cells can be charged (on) or discharged (off) as one wishes and thus they can be reused in RAM. In ROM the cells are either charged or discharged permanently. This can be represented mathematically as either l1 or 0 in the binary system or code. This storage is called a bit.

A bit stands for a binary digit. It is the amount of data stored by a computer. A bit is the basic unit of information measurement.

A byte consists of eight bits. The most common binary word length is 8-bits and is called a byte. A byte (octet) is a unit of data measurement that consists of eight bits. A 4-bit word is referred to as a half-word or nibble.

A kilobyte (KB) consists of 1024 bytes.

A megabyte (MB) consists of 1024 KB


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A gigabyte (GB) consists of 1024 MB.

CODING SYSTEMS

Coding is the process of representing numeric or non-numeric information in terms of binary digits. Non-numeric information is represented using different bit patterns such as letters of the alphabet.

Types of coding systems

ASCII

ASCII stands for American Standard Code for Information Interchange. It is a standard code for information interchange consisting of a set of 256 characters.

It is the most commonly used code for information communication, though some of the characters do other purposes like the control of printing and the system bell.

EBCDIC

Extended Binary Coded Decimal Interchange Code was most widely used on the larger computers. It employs 8-bit character emulation and at times it was referred to as the 8-bit ASCII simply because of the fewer characters it contained than ASCII.

BCD

Binary Coded Decimal code is the least used code that employs the 6-bit code. Characters are only represented with a 6-bit combination.

MOTHERBOARDThis is where the components of the system unit are mounted. It is made of fiber and does not conduct electricity. It contains the CPU, BIOS (Basic Input Output System), memory, serial and parallel ports, expansion slots, and all controllers like display screen, keyboard and disk drives.

EXPANSION SLOTS

These are sockets on the mother board into which you can plug expansion cards, or add. They are circuits on board that provide more memory space or peripheral devices.

DATA BUSES


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These are highways where data travels in the computer. They include data buses and address lines.

DISK DRIVES

Computers use disk drives to transfer programs and data between memories and disks, they work as; input/output devices. There are many types of disk drives and these include;

Floppy drive Hard drive CD-ROM drive Zip drive

POWER SUPPLY

This helps to convert power from AC supplied by the mains to DC required by computer components. It is very important, as computer circuits need power in varying amounts.

It helps in distributing power to all parts of the computer evenly. The major duties of the power supply include;

It helps in controlling and step down the in coming power. It filters and regulates power supply to the computer. It distributes power to other parts of the computer evenly.

UNINTERRUPTIBLE POWER SUPPLY (UPS)

Incase the power goes off, the UPS reserves an amount of power to enable the user save the work other wise without it, every unsaved information will be lost in case the power goes off.

OUTPUT DEVICES

These are peripheral devices that a computer uses to give out information produced after the processing operations for decision making. Computers can out put data in the form of; Graphics, Text, Sound and computer usable output. The principal output devices include: Monitor/cathode ray Tube (CRT), Printer, Plotter, Speakers/ sound system, Projector, Video display terminal, screen e.t.c.

Output devices can be classified into two categories namely softcopy and hard copy out put devices. Hard copy refers to printed output e.g. film, microfilm, paper. Hard copy output is done by printers and plotters.


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Soft copy refers to data that is shown on a display screen or is in audio or voice form. Soft copy output is done by display devices like monitors, projectors, cameras and sound output systems.

SOFT COPY OUTPUT DEVICES

MONITORSA monitor also known as Visual Display Unit (VDU) or the screen, is used to display information in form of text , pictures and video, enabling the user to monitor what is going on in the computer.Monitors are basically of three types i.e. Cathode Ray Tube (CRT), Liquid Crystal Display (LCD) and Gas Plasma Display (GPD) monitors. Monitors are connected through a video port or video adapter or integrated on the motherboard. The video adapter determines the resolution and clarity of the monitor. Examples of video adapters include: 1. Color Graphics Adapter (CGA):the oldest and displays text and images up to 16 colors.2. Enhanced Graphics Adapter (EGA): was an improvement of CGA but also displays 16 colors.3. Video Graphics Array (VGA): displays text, graphics and video using 256 colors.4. Super Video Graphics Array (SVGA): displays text, graphics and video using more than 16 million colors with a minimum resolution of 800x600 pixels.

DATA PROJECTORSThese are used to display output from a computer onto a plain white screen like a wall or white board. Projectors are a conventional way of presenting information to an audience.

LIGHT EMITTING DIODESLight emitting diodes (LED) are indicators that display light when an electric current passes through them e.g. red and green lights displayed by the system unit. They are used to give a warning like whether the computer is on or off.SPEAKERSSpeakers help to output information inform of sounds such as beeps, audio or digital. Some computers come with built-in speakers while for others external speakers are connected to a sound card through the jacks on the system unit or on a multimedia monitor.


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HARD COPY OUTPUT DEVICESPRINTERSA printer is an output device used to produce information on a piece of paper. The quality of the print out depends on the mechanism used by the printer for printing. The printers are classified in accordance to their printing mechanism i.e. impact or non impact printers.

IMPACT PRINTERSThese print using a striking mechanism. They strike the paper in order to form an imprint on it. These include dot matrix and daisywheel printers. They are cheap to run and print for a long period without breaking but they produce low quality printouts.

Dot matrix printerIt has a set of pins on the head which strikes on an ink ribbon placed over the paper.

Daisy wheel printerThis has a removable flower-like wheel having spokes with embossed characters. The wheel is rotated to align the required character and then the characters are hit with a hammer during printing.

NON-IMPACT PRINTERSThese print using ink, thermal or laser mechanisms. They are faster and quieter than the impact printers and include inkjet, thermal and laser printers.

Inkjet printersThese print by spraying tiny ink droplets onto a paper to create an image. They have cartridges with nozzles that spray the ink on the paper. Although cheap to purchase and produce quality printouts, inkjet printers are expensive to run due to the high cost of replacing the cartridges.

Thermal printersThese use thermal technology to heat ink before fusing it onto the paper. They are used in point of sale terminals to print receipts and bar codes. They are expensive to purchase or run although they produce high quality printouts.

Laser printersThese operate by shining a laser beam to create an image on a rotating drum. As the beam hits the drum, it ionizes some regions which attract ink toner particles. The toner is then fused onto a piece of paper through heating.


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Laser printers are faster compared to other printers, cheap to run and produce high quality printouts. However, they are expensive to purchase.

PLOTTERSA plotter is a large output device used to print geographical, architectural and engineering drawings e.g. maps, advertisement posters, e.t.c.

Characteristics of output devices

They can be monochrome (one color) or multicolor They are attached as peripherals into any computer They display information either in soft or hard copy Display devices can be LCD or CRT

Advantages

Enhance communication between the computer and user The user can correct errors as you work Can produce information that can be used for future use (hard copy) Facilitate information sharing. They are relatively cheap They are portable

Disadvantages

Cost of maintenance is very high Easily damaged under poor conditions Display devices can affect eye sight in the long run Some emit radiations that can cause cancer They do not store information The information can easily be lost due to power failure.

INPUT DEVICES

Refer to all hard ware components that allow a user to enter data and instructions into a computer.

Examples include keyboard, mouse, digital cameras, and microphones e.t.c

Input: its data or instructions entered into the memory of a computer.

Manual input: provides more data in put e.g. keyboard, mouse, touch screen, e.t.c.

Input devices are classified according to the way they enter data, namely: keying, pointing, scanning and other technologies employed in data capture.


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Keying devices

Keyboard

A traditional keyboard is the most common type of keying device. It is a full sized rigid keyboard. There are more portable keyboards that can be folded and packed into a bag called flexible keyboard and ergonomic keyboard which is specially designed to provide comfort and alleviate wrist strain.

Keypad

This is a miniature keyboard used on portable devices such as PDAs, laptops and mobile phones.

Braille keyboard

This is a keyboard designed for use by the blind. It has keys identified by raised dots.

Pointing devices

Mouse

A standard mouse has a ball underneath two buttons and an optical scroll button located between the left and right buttons.

An optical mouse does not have moving parts. it works by using a tinny digital camera which takes pictures. Interpreting the pictures indicates the direction of the mouse movement hence the pointer’s position on the screen.

A cordless mouse or wireless mouse is a battery powered mouse that uses radio or infrared waves instead of being physically connected to the system unit.

Trackball

Works just like a mouse but it has the ball located at the top and instead of moving the device on a flat surface, the user rotates the ball using a finger. Some computer keyboards come with an integrated trackball.

Joystick

This is a computer input device that looks like a lever used to control a pointer on the screen e.g. computer games controllers. The user controls the game actions by varying the pressure, speed and direction of the joystick. It has command buttons and triggers which issue commands or actions.


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Light pen and stylus

This operates by detecting the command or item being illuminated by it.

A stylus is used on PDAs to recognize commands or hand written data.

Scanning devices

Scanning is the process by which data is captured from an object and is converted into digital format. Scanners are classified according to the technology used to capture data i.e. optical and magnetic scanners.

Optical scanners

These capture data using optical or light technology. A light beam passes over an object and the image is analyzed by specialized software. These include;

Optical Mark recognition scanners (OMR)

These detect marks made on a piece of paper using ink or a soft pencil by passing an infrared beam over them. They are used to mark multiple choice questions, analyzing responses in questionnaires and selecting correct number combinations from lottery tickets.

Optical bar recognition (OBR)

These capture data coded as lines of varying thickness known as barcodes or Universal Product Code (UPC). These codes hold manufacturer details and product code.

Optical character recognition (OCR)

This is used to read typewritten, computer-printed or handwritten characters and transform the images into a softcopy that can be manipulated using a word processor.

Magnetic scanners

These are used to capture data written using magnetic ink or coded onto a magnetic strip e.g. Magnetic Ink Character Recognition (MICR) and card readers.

Digitizers

Also known as a graphic tablet allows a user to draw an image using a stylus. The image drawn does not appear on the tablet but on the computer screen. They are used for tracing highly detailed engineering and architectural drawings and designs.


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Digital cameras

These capture images just as cameras do though they are stored in digital form. The pictures are stored on a memory card and they can be edited, printed or uploaded to the internet.

Other input technologies

Touch screen

This lets the user to touch the screen using a finger or a stylus in order to write or select an item. The screen consists of infrared light crisscrossing behind it. When the user touches a location on the screen, the finger interrupts the infrared light and the output is displayed on the screen. Touch screens are mostly used in retail stores, airports, smartphones and PDAs.

Voice input

This is an input technology where a microphone is used to enter data in form of speech into the computer. It is commonly used for physically challenged people though does not support the related speech aspects such as accents, inflections and tones.

Interactive whiteboard

Also known as a smart board is a large interactive display that connects to a computer. The computer display is projected onto the board’s surface, where users control the computer and write using a pen or finger.

Characteristics of input devices

They are connected to the computer through ports Come as accessories and can be purchased separately Can be manual or automatic Most are plug and play Make use of drivers in order to communicate with the computer

Advantages

They are relatively cheap They are portable


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Most are compatible with different hardware They are easily accessible Communication between user and the computer is made easy They are user friendly

Disadvantages

Easily damaged with poor care Do not store data on their own Failure of an input device can bring work to a stand still. Because of portability, they are easily stolen Some are not compatible with other hardware

PROCESSING DEVICES

These are devices that read, interpret and execute instructions in order to convert data into information e.g. CPU, logical control unit

Characteristics

They are chips composed of integrated circuits. Have a clock as a control unit Posses Arithmetic and logical capabilities They reside inside the computer They are fast in processing Have storage in form of registers

Advantages

Manage flow of data in the computer They are fast in converting data into information They can carry out complicated tasks in short period of time They are automatic Process huge volumes of data with maximum accuracy They are robust

Disadvantages

They are expensive and delicate Installation and repair requires technical expertise Operation requires energy/power to run i.e. electricity The computer fully depends on it, since it the brain of a computer Technology keeps on changing, hence expensive to maintain


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SECONDARY STORAGE DEVICES

Also referred to as auxiliary storage, are hardware devices that provide long term storage for programs, data and information. They are secondary because they are not directly accessible by the CPU unlike primary storage. They can also be used for back-up e.g. Hard disk, DVD, CD, Floppy disk, Zip disk, flash disk

Characteristics of secondary storage devices

They need disk drives to read from and to be written to They function through the use of electricity (electro magnetic) They are in varying sizes and capacity Majority are random access They store information in digital format They are affected by magnetic fields.

Advantages of secondary storage devices

They are portable They are relatively cheap Make data transfer from one computer to another achievable Facilitate back-up They store huge amounts of data semi-permanently or permanently Make data retrieval faster

Disadvantages

Main agents of spread of viruses They are easily damaged with poor handling. They need disk drives to read from or write to. They need a computer to access the information in it Their disposal could cause environmental hazards

Secondary storage devices can be classified according to: portability as removable or fixed Technology used to store and retrieve data as magnetic, optical, magneto-optical and solid state.

REMOVABLE STORAGEThese are ones which are not housed inside the system unit. Data is read and written into the media using a drive. These include floppy disks, magnetic tapes, optical disks and solid state devices.1. floppy disk


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A floppy disk or diskette is made up of a thin circular plastic material coated with a magnetic recording surface where data is stored as tiny magnetic particles. Floppy disks are either double density (DD) or high density (HD) with sizes of 8 inch, 5.25 inch or 3.5 inch. The 3.5 inch HD diskettes are the most common ones.

Advantages of floppy disks

They are potable if compared to hard disks Floppy disks are cheap in terms of money. They have a high storage capacity if compared to punched cards. Data can be accessed randomly unlike the tapes that require unwinding and rewinding.

Disadvantages;

It has a small storage capacity if compared to CD, DVD, VCD and hard disk

Data can easily be lost once the magnetic media is exposed to a magnetic field.

2. magnetic tapes

A magnetic tape is made up of a thin ribbon of Mylar coated with a thin layer of magnetic material composed of iron oxide. It resembles the music cassette and data is read from or written to using a tape drive.

Magnetic tapes have disadvantages in that they are slow due to their linear storage of data and have spaces between successive data records which waste storage space.

3. solid state media

This is a non-volatile storage that employs integrated circuits rather than mechanical, magnetic or optical technology. It has no movable parts e.g. memory sticks and flash drives.

4. optical storage media

Optical storage media read and write data using a laser beam e.g. CDs and DVDs

Compact disks (CDs)These are small circular disks with a diameter of 12cm and thickness of a few millimeters with up to 700MB of storage space.


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Compact Disk-read only memory (CD-ROM) contain data that can only be read but cannot be written to. The information is stored permanently in an accessible form hence read only. Therefore the information is written on during manufacture.Recent developments in CD technology has led to CD-Rs and CD-RWs (Compact Disk Recordable and Compact Disk Re-writable) in which data can be written on and or re-written on after purchase from the manufacturers. With CD-R Once data is written on it stays permanent and becomes read only while with CD-RW data is written on, it stays on until the user decides to alter it. After writing on the CD-RW, data can be erased and new information rewritten.

Digital Versatile Disks (DVDs)These resemble CDs in every aspect but simply have higher storage capacity of up to 17GB. They are suitable for motion picture recordings such as videos because they offer better sound and picture quality than CDs.

Advantages of optical storage media

They are easy to store and they are potable.

They have bigger storage capacity compared to floppy disks

Their access speed is very fast depending on the speed of computer.

They are reliable even after 100yrs; the information will still be available

Disadvantages

Breakage or a single scratch on a CD, DVD, VCD. Can render the whole disk useless.

They can be attacked by a virus.

They can not be read by all CD-ROM drives.

Have slower access time than that of hard disks.

FIXED STORAGE

This is a hard disk or hard drive which is mounted inside the computer. However some hard disks are removable.

A hard disk is a metallic magnetic media with a read/write head housed in a protective metal case. It provides much greater a mount of data storage and it operates faster than a floppy disk.


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Hard disks are connected to the motherboard by controllers which are either Integrated Drive Electronic (IDE), enhanced IDE or AT attachment (ATA).

Advantages of hard disk

It has the largest information storage capacity. It provides immediate access to the information stored in it because the it is

built within the computer. Different types of information can be stored on it. It has the ability to protect the information stored on it. They have fewer chances of being misplaced or stolen since they reside inside

the computer case.

Disadvantages of hard disk

They are metallic, thus expand and contract depending on the changes in the temperature of the place, and this may cause data loss.

They are susceptible to virus attack, especially in unprotected systems hence data loss.

FILES

A file is a collection of related data given a name for easy access, manipulation and storage on a backing storage. Every file has a unique name, an optional extension, size, date, and time when the file was created.

Files are of three types i.e. data, system and application files.

Data files contain user specific data, system files contain information that is critical for the operation of the computer and application files hold programs and are executable.

Extension File type Description

.doc Data A Microsoft word document file

.txt Data A plain text file created using note pad or DOS editor

.tif Data A graphic file created using applications such as Adobe Photoshop.


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.exe Application file The file that launches a particular application e.g. winword.exe, PM.70.exe

.bat System file File containing a series of commands loaded during boot up.

.sys System file System file that performs fundamental operations in a computer.

FOLDERS

Also known as a directory is a named storage location where related files can be stored. A subfolder is a folder created inside another folder.

DRIVES

Storage media or devices are recognized as drives. These are given letters such as A-Z to identify them.

Storage location Drive Remarks

Floppy drive A and B If a computer has two floppy drives, one will be A and the other B.

Hard disk C,D,E,F If a computer has four hard drive, they will be assigned letters C-F.

Optical drives D,E,F,G If a computer has one hard disk and three or more CD/DVD drives, they will take up any number between D and Z

Other removable D,E,….,F If a computer does not have an optical drive, any removable drive attached to the computer can take any letter between D and Z.

Network drive Logical Network drives takes D-Z depending on the number of physical drives installed or attached.


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SENIOR TWO TERM ONE

COMPUTER SOFTWARESoftware refers to written programs or procedures with associated documentation that run on the computer hardware. When a computer processes data, it follows a particular sequence of instructions which is stored in its memory with specific details. This sequence is called a program and the preparation of such instructions is done by humans in a process called programming.

CATEGORIES OF SOFTWARE

Software is often divided into two categories:

1. Systems software : Includes the operating system and all the utilities that enable the computer to function.

2. Application software: Includes programs that do specific work for users. For example, word processors , spreadsheets, and database management systems fall under the category of applications software.

System software Application software

Operating Languages Utilities Custom Made Off-self Software

Systems & processors Software Packages

Low Level High Level

Languages Languages

Assembly Machine 3GLs 4GLs 5GLsComputer Handbook | [email protected]

Software

http://www.webopedia.com/TERM/S/database_management_system_DBMS.html

http://www.webopedia.com/TERM/S/database_management_system_DBMS.html

http://www.webopedia.com/TERM/S/spreadsheet.html

http://www.webopedia.com/TERM/S/word_processor.html

http://www.webopedia.com/TERM/S/word_processor.html

http://www.webopedia.com/TERM/S/user.html

http://www.webopedia.com/TERM/S/utility.html

http://www.webopedia.com/TERM/S/operating_system.html

http://www.webopedia.com/TERM/S/systems_software.html

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Code Code

Desktop Networking PDA others Windows2000

SYSTEM SOFTWARESoftware is a collection of computer programs and related data that provides the instructions for telling the computer what to do and when to do it. OR

This refers to a set of programs that controls the operations of the computer and its devices. It serves as the interface between the user, the application software and hardware. They provide the facilities that enhance the computer’s general performance. The system software is installed on your computer when you install your operating system.

These programs are written by the computer manufacturers or professional programmers. Some of these programs reside inside ROM and are known as firmware.

It consists of;

1. Operating System

2. Programming languages

3. Utility programs

FUNCTIONS OF SYSTEM SOFT WARE

The common function of the software includes the following;

1. It is used for shutting down the computer and restarting it.

2. It helps to detect wrong commands.

3. It is used for installing both the new hardware and the applications software

4. It helps in multi-programming

5. It controls all activities in the various parts of the computer.

6. It alerts the user and reports errors

7. Provide memory space and programs for execution.


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8. It helps to translate language; high level language codes into lower level language codes that the user can understand e.g. compilers, interpreters, linkers and assemblers.

OPERATING SYSTEMS (OS)Operating systems software refers to a set of programs that coordinate the operation of all hardware and application software components of a computer. These are programs responsible for the; Management and coordination of processes and the sharing of the resources of hardware. They make a computer easier to use because they “insulate” the user from the hardware.

When a computer is switched on, the OS program runs and checks to ensure that all parts of the computer are functioning properly. Once loaded, the OS manages all activities on the computer and interactions with input and output devices.

Functions of operating system

1. Resource location i.e. allocates processing time and memory to tasks like printing, creating a document, e.t.c

2. It helps in hardware management like accessing disk drives, printers and keyboard.

3. It helps in file management and saving the user from knowing where in memory his files are to be stored.

4. Co-ordinates the operations of all application software by enabling it interface between the computer user and the computer.

5. Helps in administering security to the computer

6. It monitors system performance.

7. The operating system coordinates the operation of all hardware and application software components of a computer

8. Data management.

9. Booting.

10. Spooling print jobs.

11. Memory management.

12. Job (task) management.


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TYPES OF OPERATING SYSTEM

Single User

Single-user operating systems allow one user to login at a time. Examples of this type are DOS and Windows 98. It allows one operation at a time i.e. you can not start creating a document and open graphics to copy the school badge at the same time.

Multi-user

It allows multiple users to log on to the system at ago. Examples are UNIX and LINUX. It allows users to access the same data at the same time. It is in used networking. Each person on the network appears to be the sole user of the computer by allocating each user on the network at a time and when the tome elapses, the next person is given a go ahead.

Multi tasking

This allows the computer to do more than one job at the same time. There is no time lag between the different tasks e.g. one can type a document as he is printing at the same time.

Networked

Is an operating system that contains components and programs that allow a computer on a network to serve requests from other computers for data and provide access to other resources such as printer and file systems. Examples are ms-windows 2000 server, ms-windows 2003 server, UNIX and Linux.

Stand alone

Stand alone are usually not connected to a network and thus cannot access networked resources.

Examples of operating systems include; disk operating system (DOS), UNIX, Windows, like window 95,98,2000, 2003, XP, Vista.

NB; The operating system commonly used on microcomputers are; Ms dos and windows

DOS is a command driven user interface which has been described by many as not being a user friendly program. It has a set of programs which help one to work with a computer effectively, merge the information on the external storage devices and carry out all house keeping routines. It is used to manage devices, command


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processing, control programs and manages system resources and errors. Examples of DOS include Personal Computer Disk Operating System (PC-DOS) and Microsoft Disk Operating System (MS-DOS).

Windows is a GUI (graphical user interface) operating system. It combines a number of features like icons to make programs easy to use. Its main aim is reliability and manageability with the help of active directory. Common examples include windows 2000,

Differences between DOS and Windows

Dos Windows

A command-line interface that takes up little memory and normally does not require a very fast processor.

Graphical user interface that needs or requires more memory as well as a faster processor.

Operation is fast because commands can be entered directly through the keyboard.

Operations in a windows environment depend on the powerfulness of the processor.

Many commands can be grouped together as a batch file so that repetitive tasks can be automated.

It is difficult to automate, functions for expert users.

Commands have to be learnt. Graphical user interface is user friendly because it is easy to learn and work with.

Commands have to be memorized. Commands need not be memorized because the commands are represented in icons and pictures.

Network operating system was designed to be used on several computers that exist on a network although at times they can be installed on stand alone computers. Common examples include Windows NT 4.0, UNIX and Linux.

PDA operating system is specifically designed for handheld computers. They are pen driven or touch sensitive and come already loaded in the computer’s ROM-BIOS.

INTERFACESWhen a computer is turned on, an interface is seen. This consists of the cursor, menus, icons, e.t.c that allow users to do things with the computer. A user interface can make a computer either easy or hard to use.


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In the designing of a user interface, sound, colors, graphics, position of items on the screen and availability of help are considered.

Types of interfaces

1. Command line

These accept commands in the form of special words or letters. The user types keywords or presses special keys on the keyboard to enter data and instructions. It provides a virtually empty screen with a blinking cursor (prompt) where commands are keyed in and the computer executes them on pressing the enter key.

The commands are accepted and executed by a part of the operating system called the command processor or command line interpreter. Command line software is more flexible but more difficult to learn. Users must have knowledge of the available commands, what they do and the rules governing how they should be typed. It is more suited for experienced users.

Examples include; DOS, UNIX, LINUX

2. Menu driven

These are many different menu forms that provide the user with a list of program commands displayed on screen and a simple means of selecting between them. It presents the user with a choice and does not need one to remember the commands. It is suitable for beginners and infrequent users.

3. Graphical user interface

A GUI allows a user to use menus and visual images such as icons, buttons and other graphical objects to issue commands. It provides a colored screen with icons each representing a program. A mouse may be used. This allows the user to enter commands by pointing and clicking at objects that appear on the screen. It makes the program easier to use.

Examples include; windows (3.1, 95, 98, 2000, win XP0, Susie Linux, Novel Netware

GUI has the following components:

Pointer; is a symbol that appears on the display screen that is moved to select objects and commands. It usually appears as a small angled arrow.


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Pointing device; is a device such as a mouse that enables the user to select objects on the display screen.

Icons; these are small pictures which represent commands, files or windows. A command can be executed or turned into a window by moving the pointer to the icon and pressing the mouse button.

Window; is a visual area containing a user interface that displays output and allows input to one or more processes. The screen can be divided into different areas running different programs or displaying a different file. Windows can be moved around the display screen and their shape and size at will.

Desktop; this is the area on the display screen where icons are grouped.

Menus; this is a program’s list of user choices or possible actions usually shown on the screen. These help in execution of commands by selecting a choice from the menu.

SENIOR TWO TERM TWO

APPLICATION SOFTWAREApplication software is software that enables a computer to perform a specific task or carry out a specific job. The job is called an application. These programs make a computer to perform different activities or uses like word processing, accounting, and graphics e.t.c. They are called application programs because they direct the processing required for the particular use of the computer and they include: word processing, spreadsheets, databases, presentations, desktop publishing, graphics processing and communication software

Application software needs a particular hardware and operating system for their operation. It is divided into the following categories:

1. Custom made/tailored/bespoke software

This is an application program which is designed and developed at a user’s request to satisfy personal data processing needs. It gives the user a chance to customize programs according to the suitable environment e.g. stock control programs, library software, e.t.c. This software is used to serve a particular purpose and no other. Such software includes school management system, banking system, insurance system, and payroll system


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2. Packaged/Off-the-shelf software

This is an application program which is copyrighted and designed to meet needs of a wide variety of users. These are of general nature and solve needs which are common in nature. They are already made programs designed to suite any environment and are bought from the shops and then installed in a computer. They include:

a. Word processing

This is used in the creation, editing, formatting, saving and printing of documents such as letters, reports, labels, poems, memos, news letters, e.t.c. word processing applications include Microsoft word, word pad, note pad, e.t.c

b. Spread sheets

These are simple grids of cells arranged in rows and columns. They are used in handling numeric data such as finance, planning, budgets, e.t.c. They include Microsoft excel, macromedia director, and lotus freelance,

c. Data bases

These are used in creation and management of large volumes of information related to a particular topic or subject e.g. mailing lists, customers and supplies. They enable the user to work with up to 15 files at once to manipulate, update and revise data to produce meaning reports. Their power comes from the ability to sort information through or from large volumes of information.

d. Presentation software

This is used in creation of computer based slide shows, overheads, e.t.c. using sophiscated graphics styles, effects, transitions and animations schemes.

e. Desktop publishing

This is used to combine graphics to create a publication e.g. brochure, prospects, booklets, business cards e.t.c. they include adobe PageMaker, Microsoft publisher, e.t.c.

f. Graphics processing

These are used in the creation and editing of graphics ranging from charts, representation graphs, paint and drawing. They include Photoshop, Microsoft photo draw, adobe illustrator, Corel draw, e.t.c


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g. Communication software

This is used in exchange of messages by sending and receiving data via computers to different areas of the world. They include software browsers like Netscape, Microsoft navigator e.t.c.

Advantages of off-shelf packages

Readily available.

They can be customized.

Cheap.

Have less error.

3. Freeware

This is copyrighted software provided at no cost to users e.g. games like Dave and solitaire, antivirus software like AVG.

4. Shareware

This is copyrighted software distributed free for the trial period and payment is required for continued use after the trial period e.g. Motorbikes, computer car driving simulations, VB NET, MySQL, antivirus software like MacAfee,

5. Public domain software

This is free software donated for public use with no copyright restriction e.g. parliament news, news papers like new vision and monitor.

PROGRAMMING LANGUAGES It refers to the means of communicating with the processor or Programming languages are mediums used by man to write instructions that command the computer hardware to perform certain tasks. They involve definition of a list of words and symbols according to a particular predetermined rule of grammar (syntax) into a logical manner to form a computer program.

There are two basic categories of programming languages. Low level and high level languages

LOW LEVEL LANGUAGES


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These are programming languages that provide little or no abstraction from the computer's architecture. They are called low level languages because they are closely associated with the processor.

There are two types of low level languages.

1. Machine code

2. Assembly code

MACHINE CODE LANGUAGE

This is a low level language in which systems of impartible instructions are executed directly by a computer's CPU. Each instruction performs a very special task. This is a first generation language and unfamiliar to humans. It is not user-friendly at all. All instructions in machine code are represented in the binary format e.g.100100100010001 on a 16 bit machine. Machine code language is highly efficient and allows direct control of each operation though it is difficult to read and debug, tedious, time consuming, error prone and designed for a specific machine and microprocessor.

ASSEMBLY CODE

This is a low level language in which each statement corresponds to a single machine language instruction. They are always specific to certain computer architecture and allow the use of symbolic representation for machine codes. This was invented to assist machine code programmers. It is more easily under stood and remembered by humans e.g. SUB for subtract, FNO for first number. It has a closer control over the hardware and executes efficiently but it is designed for a specific machine and microprocessor.

Low level languages are closer to the hardware than are high level languages which are closer to human.

HIGH LEVEL LANGUAGE

A high level language is an advance computer programming language that is not limited b the computer or for one specific job and is more easily understood. These were introduced as a further refinement in the assembly language. They make programming much easier to use. In high level language, fewer instructions are written and therefore a lot is done in less time. They are user-friendly and problem oriented since they involve wide vocabulary of words, symbols and sentences. They are used in conjunction with their syntax.


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There are over 500 high level programming languages which include the following.

COBOL; common business oriented language. This was designed for business and commercial processing. COBOL is widely used because it is compatible to different types of computers and a pool of skilled programmers.

FORTRAN; formula translation. Is usually used in processing numeric data in scientific and engineering applications.

BASIC; beginners all purpose symbolic instruction code. This can do almost all computer processing tasks. It is used to teach students how to use computers.

PASCAL. This is used for teaching programming. It uses procedures and functions which allow a top-down approach to solving problems.

HTML; hypertext markup language. Is one of the main programming languages used to create web pages for the internet or intranets

JAVA; This is an object oriented programming language that displays graphics, accesses the network and interfaces with users via classes that define similar states and common methods for an object’s behavior.

4GL’s (fourth generation languages); these were designed to make programming much more easier. They consist of pre-defined functions and procedures which need little customization before they can be used.

5GL’s (fifth generation language); these types of languages are normally used in intelligent knowledge based systems (1 KBS) such as robots. They manipulate facts and rules to reach a conclusion. Thus they “think” just like humans and are commonly used in artificial intelligence projects like exploration.

LANGUAGE PROCESSORSA language processor is a hardware device designed or used to process program code to machine code. Language processors are mainly used with high level programming to work backwards to the processor. Their main work is to translate high-level language codes into low-level language codes that the processor can understand.

A translator on the other hand is a program that accepts text expressed in one language and generates semantically equivalent text expressed in another language.

Language processors include;

1. Compilers


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2. Assemblers

3. Interpreters

4. Linkers

Compilers

These translate a program written in high level language into machine code or into assembly code program. The entire program is translated into machine code at compilation time. They do the following.

Allocate areas of main storage.

Generates the object program on cards, tapes, or disc as required.

Produces a print listing of the source and object programs when required.

Tabulates a list of errors found during compilation, e.g. the use of ‘words’ or statements not included in the language vocabulary.

Assemblers

An assembler is a program that translates assembly language/ instructions into binary code or machine code, a format that is understood by the processor. They normally begin from where compilers stop. They do the following.

1. Assemblers allocate areas of storage.

2. Detects and indicates invalid sources-language instructions

3. Produces the object program on cards, tapes, or disc as required.

4. Produces a print listing of the source and object programs with comments.

5. Data may be added to tell which program may be executed first.

6. This program can only be executed when the assembly process is completed

7. Translates mnemonic operation codes into machine code, and symbolic addresses into machine code

Interpreter

An interpreter translates high level instructions into an intermediate form which it then executes. The source program is translated line by line while the program is


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running. As a result a program running under an interpreter runs very slowly as compared to a compiled program.

It does not need to go through the compilation stage, the interpreter immediately executes high-level programs and thus it is faster.

Linkers

These programs combine compiled programs and determine where the program will be located in memory. When the linker has transformed an object code, an executable file is generated. This normally results in files with the extension.

UTILITIES

A utility is a program that performs a specific task related to the management of computer functions, resources or files like virus protection, memory management, password protection and file compression. Utilities are also called service programs and they are used to enhance the performance of the operating systems. These programs are part of system software used to support, enhance or expand existing programs in a computer system and make it more and more user friendly.

The most common utilities Include.

1. Debuggers; used during the testing of programs and locating errors

2. Sorts; used for data sorting

3. Editors; for making changes, used for word processing

4. Resource; used in networks

5. A disk scanner utility-it detects and corrects both physical and logical problems on storage devices

6. A disk defragmenter utility-it recognizes the files and unused space on a computer’s hard disk

7. An uninstaller utility- it removes an application as well as any associated entries in the file system

8. A backup utility- allows user to copy or backup selected files onto another storage disk

9. Data recovery utility- recovers accidentally deleted files from your computer.


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10. An antivirus utility. It prevents, detects, and removes viruses from a computer’s memory or storage device.

11. A screen saver utility- is a utility that causes the monitor’s screen to display a moving image or blank screen if no keyboard or mouse activity occurs for a specified period of time.

Screen savers originally were developed to prevent a problem called ghosting, in which images could be permanently etched on a monitor’s screen.

Screen savers can be used for reasons of security, prevent unwanted on lookers from accessing information or data from your computer, for advertisements on the screen, for entertainment and also prevent burn in.

VIRUSESA computer virus is a potentially damaging computer program that copies itself into other programs and spreads through multiple computers. OR

A virus is a malicious logic program acting without the user’s knowledge and deliberately alters the computer’s operations.

A bomb is a program routine that destroys data when certain conditions are met.

A bug on the other hand is an error in a program that causes it not to work.

It spreads throughout the system to create unwanted effects such as damage to programs and operating files, corruption of data files, slowing down the computer and so on. Viruses are often designed to affect, or infect, a computer negatively by altering the way it normally works without the knowledge or permission of the owner.

They usually carry out the following;

Attach themselves to another program or a file.

They spread themselves from one computer system to another.

Locate themselves with in the computer system in such a way that it interferes with the normal process of the OS.

Types of viruses

A worm: copies itself repeatedly in memory or on a disk drive until no memory or disk space remains, which makes the computer to stop working. This fills the


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storage space with garbage files, uses up resources and at times shuts down the computer or network.

Boot sector: Executes when a computer starts up because it resides in the boot sector of a floppy disk or the master record of a hard disk.

File virus: Attaches itself to program files and is loaded into memory when the infected program is run.

Macro virus: Uses the macro language of an application (e.g. word processor or spreadsheet) to hide the virus code. Macro is a symbol, name or key that represents a list of commands, actions or keystrokes. They can be used to enter words or phrases that are frequently used.

Logic bomb: Is a virus that activates when it detects a certain condition.

Time bomb: Is a kind of logic bomb that activates on a particular date.

A Trojan horse: hides within or looks like a legitimate program. Unlike a virus or worm, a Trojan horse does not replicate itself to other computers but a certain condition or computer action triggers it.

Polymorphic virus: Modifies its program code each time it attaches itself to another program or file, so that even an antivirus utility has difficulty in detecting it.

Destructive viruses

Type of destruction Symptoms

Massive destruction Attacks the formats of disks whereby any program or damage will be unrecoverable.

Partial destruction Erase and modification of a specific portion of disk affecting any files stored in that location.

Selective destruction Erase and modification of specific files or file groups.

Random havoc Randomly changing data on data or in memory during normal program execution, or changing key stroke values, or data from other input/output.

Network saturation Systematically using up memory or space to impede performance or cause the system to crash.


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Non-destructive viruses: these do not cause any destruction, but are annoying. They display messages, change display colors, change key stroke values e.t.c.

Symptoms of viruses

1. Slower than normal program operation.

2. Slow-down of the general system.

3. Unusual and frequent error messages or images.

4. Change in file size.

5. Loss or change of data.

6. System crash.

7. Randomly playing music or unusual sounds.

8. Save operation does not actually save.

9. Files become corrupted.

10. Programs or files do not work properly.

11. Mysterious files, often with alluring (appealing) names, suddenly appear with enticing messages.

12. System properties change.

13. Less storage and RAM memory than expected.

Ways in which viruses enter into a system

Pirated software. The use of pirated software introduces the risk that the software may be contaminated by virus code or amended to perform some other destructive function which may affect the computer system.

Fake games. Many people like playing games on computers and for the same reason games programs spread very fast. These games keep infecting systems as they are installed. Such games are normally irresistible.

Freeware/shareware. Both freeware and shareware programs are commonly available from bulletin board system (BBS). Generally a registered fee is required to be sent directly to the author. Such programs should be treated with


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caution and initially used in a controlled environment until it is clear that the program actually does what it is supposed to do and does not contain either virus or destructive code.

Contact with contaminated systems. Any diskette used on a contaminated system could become contaminated. If the same diskette is used on another system, then the virus will spread.

Updates of software. These are distributed via the internet or other networks. Software distributed via Netware fairly obvious targets for virus programmers, as they provide a built in method for widespread and anonymous propaganda.

Infected proprietary software. There have been instances of virus programs being introduced and contaminated software under development in laboratories and then being installed into diskettes containing the finished software product. Although recorded instances are still low.

Hacker’s intent on malicious destruction of networked systems to which they have gained unauthorised.

Using infected disks from vendors, consulting firms, computer repair shops and mail-order houses.

Downloading and opening infected files from the internet.

Protection against viruses

Always have a memory resident anti-virus software that is continually updated usually with downloads from the internet.

All software and data files should be backed up regularly. This can be of help in the event of a system failure.

Users should avoid using programs of unknown origins.

There must be a policy which educates the users on the danger of viruses.

Ensure that the e-mail is from a trusted source before opening or executing any e-mail attachment.

Never start up a computer with a floppy disk in the floppy drive.

Write-protect the recovery disk before using it.


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Not sharing diskettes.

Ensure that there is a policy to ensure the usage of computers and their protection and regulations.

Set the security level for macros in an application so that the user can choose whether or not to run potentially unsafe macros.

All unlicensed software should be carefully examined before use.

Always check for viruses on portable disks when used to move files between computers.

Backup important files regularly.

Antivirus

Is a utility program that prevents, detects and removes viruses from a computer’s memory or storage devices.

Software antivirus guards include: Norton, F-secure, McFee, AVG, Kaspersky, Avira, thunder byte, penicillin e.t.c

An antivirus scans for programs that attempt to modify the boot program, the operating system and other programs that are normally read from but not modified.

Antivirus utilities normally look for virus signatures to identify a virus. A virus signature, or virus definition, is a known specification of virus code.

Users of antivirus utilities must update the virus definition files as often as possible to ensure that such files contain patterns for newly discovered viruses.

However, a polymorphic virus modifies its program code each time it attaches itself to another program or file, so that even an antivirus utility can not detect it by its virus signature. Antivirus utilities may also detect viruses by inoculating existing program files.

To inoculate a program file, the antivirus records its file size and file creation date in a separate inoculation file, and uses this information to detect if a virus has altered the inoculated program file.

However, a stealth virus infects a program file, but still reports the size and creation date of the original, uninfected program.

If an antivirus utility can not remove the virus, it often quarantines the infected file in a separate area of a hard disk until the virus can be removed.


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Most antivirus utilities can create a recovery disk to remove or repair infected programs and file e.g. boot sector virus

In extreme cases, a hard disk may need to be reformatted to remove a virus.

A backup copy is thus made and should be kept in a fire proof and heat proof safe or off site.

Files can be restored by copying the backed up files to their original location on the computer.

A back up is a duplicate of a file, program, or disk that can be used if the original is lost, damaged or destroyed.

Hacking

Hacking is the unauthorised access into a computer system. A person logs onto a computer as though he/she is someone else. This may cause copy of data, modification or deleting of data and looking at data.

Protection against hacking

1. Logging off correctly from the computer when leaving the machine.

2. Choosing passwords that are not obvious.

3. Keeping passwords confidential and not writing them down anywhere.

4. Changing passwords frequently.

5. Use of authentications such as finger prints and voice recognition for highly sensitive data like for the military.

6. Encrypting data that is transmitted.

Encryption is a means of scrambling data so that it can only be read by the person holding the encryption key which is a list of codes for translating encrypted data.

Files that contain sensitive data are encrypted or coded. If a tape or disk containing sensitive files is stolen it would then be impossible to read the data without a decoder

Encryption is also used when important data is transmitted from one place to other. The data is coded before being sent and then decoded at the other end. Both processes are performed automatically by computers. When people are making


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payments for goods bought over internet using a credit or debit card the details are always encrypted

Computer errors

A computer error is the occurrence of an incorrect result produced by the computer. They are caused by:

User errors such as incorrect entry of data values or pressing the wrong keys.

Users accessing the files or parts of applications that they are not supposed to.

Program bugs i.e. errors in the logic of the program.

Protection against computer errors

Users should be trained to use applications properly in order to minimise data errors.

Computer programs should be made user-friendly so that any user errors are trapped and the user has a chance to correct them.

Software should be tested thoroughly to ensure that it is bug-free.

User access levels should be properly defined to ensure that users do not accidentally or purposely access files or data that they are not authorised to access.

THEFT AND SYSTEM CRASHES

Data and information can be lost if computers are stolen or the hardware crashes. In order to protect a computer against theft and system crashes, back up of data and applications on a regular basis is important.

Backing up provides means of information restoration quickly and accurately. Failure to back up data may lead to loss of data, loss of hardware and reprocessing effort due to lost data.

Computer crimes

Trespass


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Trespass is when someone is able to connect to a computer and control it in some form. This can range from being able to view or access files or run programs on the computer.

Tracking

Tracking in when someone is able to monitor what the other is doing on a computer system. This applies mostly to internet usage where one can monitor which sites you visited or which links where clicked so that they may be able to determine your interests.

Tapping

Tapping is when someone gains access to information that is being transmitted across communication links.

Sabotage

Sabotage is when a malicious user renders a system unusable by other users. This can be through hacking or denial of service.

Spam

Spam is unsolicited (unwanted) junk e-mail. It is usually annoying, but usually harmless and clicking to these links may sometimes leave your computer open to hackers or crackers.

DOWNLOADING AND UPLOADING

Down loading refers to the retrieving of files from another computer and storing them on your computer on a network.

Uploading refers to the sending of files from your computer to another computer on a network.

BOOTINGBooting or booting up is the process of turning on of a computer system and preparing it to perform normal operations. It involves loading programs and the operating system into main memory.

There are two types of booting;

Cold booting; this refers to starting up of a computer from a powered down or off state.


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Warm booting; this is the process of restarting of the computer that is powered on.

A warm boot is the process of restarting, or resetting, a computer that is already turned on. This is done either by pressing the restart button or by pressing a combination of keys (Alt + Ctrl + Del).

Both types of booting clear out the bugs (errors/mistakes), failure of the computer programs, bombs, e.t.c

Steps followed when booting

1. The internal power supply turns on and initialises. The power supply takes some time until it can generate reliable power for the rest of the computer because having it turned on prematurely could potentially lead to damage.

2. When the reset button is released, the processor will be ready to start executing instructions and finding the BIOS (Basic Input Output System) program. This is called the POR (Power-On-Reset)

3. The BIOS performs the Power-On-Self Test (POST). It is accomplished using firmware program held in a ROM chip mounted on the motherboard. It checks basic input and output devices such as the keyboard, monitor and the mouse.

4. After POST, the computer reads instructions such as the current time and date from a special memory known as the Complementary Metal-Oxide Semi-conductor (CMOS). CMOS is powered by a dry cell and if the cell is down, the computer requires the user to enter the current time and date.

5. Finally, the Operating System (OS) is loaded to the computer memory.


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COMPUTER NETWORKINGA computer network is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information. A computer network is formed whenever more than one computer is connected together. Computer networks usually have one computer reserved as the server or “Mother” of all the computers on the network. Usually there can from two to hundreds or even thousands of computers on the network. Apart from computers, other network devices such as printers, plotters, etc can also be connected to the network.

Server

The server is the host or central computer that manages the resources on a network. It enables information and network devices to be shared among the computers on a computer network.

A server can serve specific requests from users. For example, you can have a file server that becomes a central storage place and manages files for your network, a print server that takes in print jobs and ships them off to a printer, a database server that stores and provides access to a database and a network server (e.g. a DNS) that manages network traffic.

A server provides many benefits that includes;

Optimization : server hardware is designed to quickly serve requests from clients.

Centralization : files are in one location for easy administration.

Security : Multiple levels of permissions can prevent users from doing damage to files.

Redundancy and Back – up : data can be stored in a redundant way making for quick restore in case of problems.

The server is a computer with a higher hard disk and main memory (RAM) capacity than the other computers on the network. It also supports multiple processors, has faster input and output, and has fast network cards.

Bandwidth

The rate of speed of data through a channel and is expressed in bits per second. The bandwidth is the difference between the lowest and highest frequencies transmitted.


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NETWORK TYPESComputer network are generally classified into:

Local Area Network (LAN) Metropolitan Area Network (MAN) Wide Area Network (WAN) Intranet Extranets Internet

LOCAL AREA NETWORK (LAN)

This is a network that connects computers and devices in a limited geographical area such as a home, computer laboratory, office building, e.t.c. LAN is formed whenever several computers in the same building or locality, are interconnected by, say, coaxial cables, and can efficiently share data and other resources. They are characterised by low cost and high data rate transfer, smaller geographical range and no need for leased telecommunication lines.

Present day wireless communication LANs are based on Ethernet technology. Ethernet belongs to a family of connection protocols described by a set of standards together called IEEE 802 which are published by the Institute of Electrical and Electronics Engineers,

WIDE AREA NETWORK (WAN)

This is a computer network that covers a large geographical area such as a city, country or even spans intercontinental distances using communication channels that combine many types of media such as telephone lines, cables and air waves.

This is where by computers in different sites are interconnected. These computers can be several Local Area Networks linked to each other over long distances (e.g. across states, entire country or entire world). This can be done by means of telephone links or a satellite link.

Companies use a WAN to connect various company sites so that information can be exchanged between distant offices.

METROPOLITAN AREA NETWORK (MAN)


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This is a large computer network that usually spans a city or a large campus. MANs cover geographic areas within a radius of approximately 10km.

THE INTERNET

The internet is a world wide collection of networks linked together. It is a global connection of computers where by access to information world wide is enhanced.

The Internet consists of a multitude of interconnected networks both large and small. At the edge of this giant network is the individual consumer computer.

On the internet, the different computers can be accessed by means of software browsers like Netscape or Microsoft Navigator. The basic requirements to connect to the internet are; a modem and telephone lines.

INTRANETS

This is a set of networks, using internet protocol and IP based tools such as web browsers and file transfer applications, which are under control of a single administrator. The administrator closes the intranet to all but specific, authorised users. It's an internal network of an organisation.

Intranets are a small version of the internet used within an organisation. They use TCP/IP protocols, which supports multimedia web pages and is accessible via a Web browser. It generally makes company information accessible to employees and facilitates working in groups. An intranet is a network similar to the Internet but only accessible from within a site (school, company, government department etc).

An Intranet is a company-wide network run along the lines of the World Wide Web. This makes it possible to share documents, databases and applications

This saves wasting time browsing aimlessly through thousands of files and also enables unsuitable material to be screened out. Example: A school may have an intranet which pupils can access for information from any networked computer. Nobody outside the school can look at the intranet

EXTRANETS

An extranet is a network that is limited in scope to a single organisation and has limited connections to the networks of one or more other trusted organisations.

Extranets are much wider in terms of area of span than the WANs. Extranets can cover regions or continents but their accessibility is only limited to those authorized to do so. For example if the Uganda government connect all its embassies abroad on a single network, then this arrangement is called an extranet.


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CATEGORIES OF COMPUTER NETWORKSA network links two or more computers systems together in order for them to be able to share resources and peripherals like, disk drives, printers, software and data.

Networks may be in two categories;

Peer to peer Network

Client to server Network

PEER TO PEER NETWORK

In this type of network, several personal computers are connected together, with each being able to access the resources of other computers. All machines on a peer to peer network are equal. There is no single machine that is designated as the main computer or central point or controller. The simplest peer to peer network is where two PCs are connected together to share the same resources.

CLIENT SERVER NETWORK

In this type of network several computers are connected to a single central computer or server, which controls all the resources. The server controls communication and shared network resources. The client machines are individual user workstations connected to the network.

Client workstations

These are personal computers (PCs) attached to the network, on which the network users do their work. The workstations have their own operating systems and files. Usually there can be two or even hundreds of client workstation on the LAN.

REQUIREMENTS FOR NETWORKING COMPUTERS1. Network Interface Cards2. Hub/Repeater3. communication media ( cables) 4. Computers5. Routers6. Networking operating system software

Network Interface Cards


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This is a piece of computer hardware designed to allow computers to physically access a network. Network Interface Cards (NICs) enables each computer on the network to be connected to the network cable. They are usually installed in the expansion slots in the server and the workstations.

Every card must have a network card driver (software) loaded in the computer, which provides the communication between the card and the network operating system software. The performance of the NIC depends on the card bus width and the speed of the card.

Each NIC has a unique address which is stored on the card that allows any device to connect to the network without creating an address comflict.

Hub/Repeater

A hub is a device that connects and amplifies digital signals from one computer and transmits them to all computers in the network. A Repeater is a hub that amplifies analogue signals.

Bridges

This is a device that connects multiple similar network segments at the data link layer.

Switch

This is a bridge with numerous ports.

Routers

This is a device that forwards data packets between computer networks by processing information found in the datagram or packet creating an overlay inter-network. A router is connected to two or more data lines from different networks. When a data packet comes in on one of the lines, the router reads the address information in the packet to determine its ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey. Routers perform the "traffic directing" functions on the Internet. A data packet is typically forwarded from one router to another through the networks that constitute the inter-network until it gets to its destination node.

Gateways

This is an internetworking system capable of joining together two networks that use different base protocols. A network gateway can be implemented completely in software, completely in hardware, or as a combination of both.


http://en.wikipedia.org/wiki/Internet

http://en.wikipedia.org/wiki/Routing_policy

http://en.wikipedia.org/wiki/Routing_table

http://en.wikipedia.org/wiki/Internetwork

http://en.wikipedia.org/wiki/Internetwork

http://en.wikipedia.org/wiki/Computer_network

http://en.wikipedia.org/wiki/Data_packet

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COMMUNICATION MEDIAThese are the physical or wireless pathways used to transmit data and information from one computer to another. They include cables, radio waves, microwaves and satellite.

CABLES

These are the media (or path) used to connect computers together in a network. They are generally referred to as “transmission media” since they are the paths on which data signals travel from one computer to the other in the network.

In the LAN there are four types of transmission media

1. Twisted pairIt’s the most widely used cabling system in Ethernet network. Two copper wires are twisted in pairs around each other to form the twisted pair cable. They are separately insulated and can not exceed 100 metres without a repeater. These cables are mostly used in fixed telephone lines without a building and local area networks in the range of 10mbs-100mbs.

Advantages They are cheap to install. They are easy to set up and maintain

Disadvantages Low data rate i.e. small amounts of data per second Short range Limited bandwidth Susceptible to interference and noiseTwisted pair cables come in two forms i.e. Unshielded Twisted Pair (UTP) and Shielded Twisted Pair (STOP).(a) Unshielded twisted pairAdvantages Lowest cost of purchase Very simple to install Low installation costDisadvantages Prone to electromagnetic interference Lowest in bandwidth Less secure


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(b) Shielded twisted pairAdvantages Moderately low electromagnetic interference Higher bandwidthDisadvantages They are more expensive to set up compared to UTP More difficult to install They are thick and heavy hence not portable Usually found in older networks.2. Coaxial cableIt is the most versatile media used in telephone in television systems, office buildings and other sites of LANs. It is used in long distance telephone transmission to carry up to 100000 voice calls simultaneously and can be used in short distance computers.The cable consists of copper or aluminium wire wrapped with insulating layer typically of flexible material surrounded by a conductive layer.Advantages High bandwidth Moderate electromagnetic interference Used as back bone cableDisadvantages They are quite expensive Installation costs are moderately high3. Optical fiber cablesThis is a flexible, transparent fiber made of a pure glass (silica) not much wider than a human hair. It functions as a wave guide or light pipe that transmits light between the two ends of the fiber. Optical fiber cables are not affected by electromagnetic radiations and have the highest transmission speed.

Cable Connectors

There are a number of different types of cable connectors depending on the type of cable to be connected. RJ – 45 connectors are the sockets used for twisted pair LANs.

MICRO WAVES

These use earth based transmitters and receivers to relay data. There equipments look similar to satellite dishes.

SATELLITES


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Satellites use microwave radio as their telecommunications medium which are not deflected by the earth's atmosphere. Satellites are stationed in space and orbit the earth receiving and relaying voice, data and TV signals.

INFRARED

Infrared communication transmits signals between devices with in small distances of no more than 10 metres.

NETWORK TOPOLOGIESNetworks can be arranged in many different ways, called topologies. Some networks are connected together physically, whereas others, such as those making use of radio, infra – red or satellite links, have no connections as such but behave as if they were connected by wires.

A network topology is the layout of the interconnection of computers in a computer network. The main topologies in use are ring, bus and star.

The ring topology

This is a network topology in which all the computers are connected in a circle with a break for each computer. Each computer is connected to its left and right neighbouring computer such that all computers are connected to each other and data can reach another computer either left or right-wards.

Data passes around the network in one direction. As each computer receives data, it checks to see if the data is for that computer and if not it sends the data on to the next computer.

The advantages of ring topology are;

1. considerable saving on cabling cost

2. High speed unidirectional communication

However the disadvantage is that if any computer breaks down, the ring circuit is broken, and communication between any of the other computers cannot take place.

The bus topology

This is a network topology in which all the computers are connected to a single common cable, which is often called the backbone. The bus topology is sometimes called a line topology.


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Signals are normally passed in either direction along the backbone. At each end of the cable there are terminators. These prevent signals that have reached the end of the cable from reversing direction and interfering with the other signals.

As can be seen, it is not possible to use very long lines with a bus topology and thus suitable for small LANs. If there are too many users on the network, the service could be slow.

The star topology

This is a network topology in which all computers are connected to a special central computer called the server. A star network topology normally exists in client-server network links where by the different computers (workstations) are connected to a central server to access the necessary shared resources.

The communication between any two workstations is via a server. If a wire between a computer and the server break or develop a fault, the rest of the network remains operational.

The disadvantages of this network is that

1. It is more expensive because it uses more cables2. If the central server fails to work then the whole network will stop working.

Other Topologies Includes;

An extended star topology links individual stars together by connecting the hubs and/or switches. This topology can extend the scope and coverage of the network.

A hierarchical topology is similar to an extended star. However, instead of linking the hubs and/or switches together, the system is linked to a computer that controls the traffic on the topology.

A mesh topology is a network topology in which each computer is connected to all the other computers on the network. It is implemented to provide as much protection as possible from interruption of service. The use of a mesh topology in the networked control systems of a nuclear power plant would be an excellent example. As seen in the graphic, each host has its own connections to all other hosts. Although the Internet has multiple paths to any one location, it does not adopt the full mesh topology.

Advantages of networking1. It provides easy and faster communication facilities. Using a network, people

can communicate efficiently and easily via email, instant messaging, chat rooms,


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video telephone calls and video conferencing.2. It enables different people to share information. In a network environment,

authorized users may access data and information stored on other computers on the network.

3. Sharing network and computing resources. In a networked environment, each computer on the network may access and use resources provided by the devices on the network, such as printing document on a shared printer.

4. It encourages and promotes group work.5. Information is created and stored safely.

Disadvantages of networking1. There is no privacy of information.2. In case the server fails the entire network comes to a stand still. This may lead to

all the workstations remaining redundant.3. Some users can misuse the resources. 4. Viruses can easily be transmitted to the machines. This may be in form of

hackers who can use viruses or worms to either destroy data or prevent access to the network or its devices.

5. A computer network may be too hard to set up or costly.

NETWORK CONNECTION TYPESFor various devices to exist in a network, they must be connected. Two types of connections are involved;

Physical connection Logical connection

Physical connection

In order for resources and information to be shared on a network, server, workstation and other devices must be physically connected by use of network card, the cable is used to provide communication pathway.

The physical connection determines the kind of cable to be used and the mode of information transmission over cable.

Logical connection

After physical connection, before accessing the network services, logical connections must be made. This is carried out by logging on to the network server by the software programs. Before connecting on to the server one must prove that she/he is authorized user, by providing a user password to the server. When the


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server accepts the password, then you are an authorized user, if it rejects it then you are not authorized.

NETWORK SECURITYNetwork security is the authorisation of access to data in a network, which is controlled by the network administrator. It is done by assigning ID and passwords that allow access to information and programs with in authority.

It consists of the provisions and policies adopted by the network administrator to prevent and monitor unauthorised access, misuse, modification or denial to the computer network and access to resources.

Most networks have several levels of security which include;

1. Login and password security2. Serve security3. File system security.4. Firewall5. User name and password

Login and password security

This controls who can access the network. If a person tries to log in with a wrong password, the server can decide to shut down that computer, therefore it is the duty of the work administrator to;

Assign user names to all users

To assign password to all user names

To control network resources by restricting where and when to log in

Detect intruders who attempt to use stations without correct password

Prevent un authorized access to the server control

SERVER SECURITY

This controls access to the server console (monitor). This is controlled in three ways;

1. Supervisor/administrator rights; these are granted to specific users who have rights to use the console (monitor)

2. Directory rights; these are granted only to those specific users who will have access to the system directory where key server files are stored.


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3. Server utility; these include utilities such as monitor and secure console, which are used to prevent un authorized access to the server console.

File system security

File system security consists of;

➢ Rights security

➢ Attributes security

Rights security

Help to control what a user may be allowed to do on the network directories and files.

Attribute security

This assigns various characteristics to individual directories and files. Attributes can be used to prevent users from; deleting a file, copying a file, viewing a file, writing to a file e.t.c.

FIREWALL SECURITY.

A firewall is special software or hardware designed to protect a private computer network from unauthorized access. A firewall filters information coming from the internet and connecting into your personal computer or network. It typically rejects access to requests from unsafe sources while allowing actions from recognised ones. They play a vital role in network security with the increased rate of "cyber" attacks to prevent planting viruses, stealing/corrupting data, e.t.c.

Firewalls are used by corporations, banks and other big organizations to keep information secure and safe by preventing unauthorised remote logins, limit or stop spam and filter the content that is downloaded from the internet. They can also offer virus protection though anti-virus software on each computer is worth installing for better protection.

NETWORK USERS

They are identified as authorized network users. They are divided into four categories; regular network users, operators, managers, and network supervisors.


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COMPUTER MAINTENANCEThis refers to caring, catering for a computer with a purpose of preserving, keeping it in good working order, and to prevent any damage.

TYPES OF MAINTENANCE

Hardware and software maintenance

Preventive maintenance

Routine /regular/ frequent maintenance(it is timetabled e.g. weekly, monthly, annual)

Prompted /unprompted maintenance ( if there is problem)

Importance of computer maintenance

To enable a computer serve for a long time

To enable a computer operate at its designed capacity.

To prevent a computer from total break down leading to lose of all information.

To reduce associated costs for repairing and risks

To prevent / avoid abrupt/ unscheduled break down of computers that can lead to loss of information

FACTORS TO CONSIDER IN COMPUTER MAINTENANCE

1. Type of computer, manufacturer e.g. IBM compatible, Macintosh, Toshiba, tropix and its processor speed; e.g. Pentium I,II,III Iv

2. Tools to apply e.g. blower, liquids, brushes, pliers etc.

3. Type of problem; is it hardware or software problem

4. Environment of the computer; office, school lab., public place etc

5. Operator/ user; is it personal or shared computer.

6. Whether the system is networked or not

7. Type of software; operating system, type package it has.

8. Type of room where the computer is kept. Is it air conditioned, venerated or not.Computer Handbook | [email protected]

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DATA SECURITY AND CONTROLData security is the protection of programs and data in computers and communication systems against unauthorised modification, destruction, disclosure or transfer, whether accidental or intentional.

Data control is the various measures taken to enforce the security of the programs and data.

Data can be lost in various ways such as viruses, user errors, computer crashes, hacking e.t.c.

COMPUTER SECURITY

Computer security is concerned with taking care of hardware, software and data.

Loss of data can have various consequences which may include:

Bad business decision

Loss of goodwill from customers

Cash flow problems

Adverse publicity from the press

Late delivery of goods

Failure to receive payment

Physical security

Computer equipment and its data need to be protected from physical harm. These include natural ones such as Fire, Lightning, Water damage, Theft e.t.c

Protection from fires

Fireproof doors help contain fire

Use Smoke detectors

Use gas folding systems are used in large computer installations

Protection from dust and extremes of temperature

Air conditioning is more important for larger mainframe system where the temperature and humidity must be controlled


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The air must also be pure and filtered in this way

Computer theft

There are many ways of making sure that unauthorized people are denied access to a system through use of keyboard locks and password. It is more difficult to prevent a thief from picking up a system and stealing it. Locks alarmed on circuit board and tags are method of hardware protection.

Preventing theft

Note the serial number of computers and peripherals

Lock the computers in case and key should be safely saved

Data should be backed up regularly

All staff aware of security

All staff wear security badge which contains their photograph, name

Software security

The vital part of a computer is the data. Data suffers from a number of risks and great care is expected to be adopted to protect against them.

The risks to data are;

Accidental loss.

Accidental damage or corruption.

Theft.

Deliberate damage or corruption.

Authorized disclosure.

To guard against these risks, the operator must make sure that:

1. Makes backup copies of the data regularly. Before backing up make sure that the data is error free otherwise you might take up a back copy of corrupted data.

2. Minimize the number of visitors to your computer installation and do not allow any one to your server except the network administrator.

3. Avoid diskettes coming from different installations as your system might contract viruses.


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4. If you have unwanted printouts, destroy them because data is not supposed to fall in unauthorized hands.

5. Save data regularly as an abrupt power cut off may corrupt your data, if you have no UPS.

THE INTERNETInternet is the global connection of computers where by sharing and access to information world wide is enhanced. It is a world wide collection of networks linked together And the largest wide area network (WAN) in the world. It consists of many different types of computers based on a common language which allows all these computers to talk to each other. It is the world’s largest computer network, the network of networks, which is scattered all over the world linking schools, homes and businesses together.

The internet comprises of hardware that sends data from place to place through cables and computers, and software that glues the system together. It consists of millions of computers connected to one another. It is composed of many interconnected computers, enabling them to share information with one another and to share resources such as super computers and data bases information.

The internet has made it possible for people all over the world to effectively and inexpensively communicate with one another. It allows interconnection of any kind of computer network.

There are four basic building blocks of the internet i.e. host, clients, routers and connections.

Host: any computer on the network that is used as a storehouse for services available to other computers on the network. In most cases it is one host machined providing several services such as WWW and USENET.

Clients: these are computers which are connected to the host in one network. Clients on a network send E-mails, upload/download files ad access the World Wide Web. This is done by sending data in form of packets which are sent with both the return and destination address.

Routers: this is a special device that seats at key points on the network and acts a traffic cop at an intersection of hundreds of streets. It reads the destination address of the packet being sent and forwards the packet to the appropriate destination. In some cases, data travels through several routers before reaching its destination.


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Connections: this combines several different types of technologies including; dial up phone lines, fiber optics, ISDN, frame relay, satellite links, e.t.c.

HISTORY OF THE INTERNETThe internet started in the 1960s as a way for the government researchers to share information as a solution to world war problems. Computers in the 1960s were large and immobile and in order to make use of information stored in any one computer, one had to either travel to the site of the computer or have magnetic computer tapes sent through the conventional postal system.

This eventually led to the formation of the ARPANET (Advanced Research Projects Agency Network) which evolved into the internet. This was in 1969 after a first test network was set up in Great Britain.

ARPANET was a great success but membership was limited to certain academic and research organizations who had contracts with the Defense Department. This project used four high-speed super computers with high-speed transmission lines to transfer data on its network. In response to this, other networks were created to provide information sharing.

In 1970’s ARPANET’s Network Control Protocol (NCP) developed into Transmission Control Protocol/ internet Protocol (TCP/IP) a more sophisticated standard. This enabled messages to be broken down into smaller “packets” sent across the network and on reaching the destination it was assembled into the original message before it could be opened. .

ARPANET was aimed at allowing multiple users to send and receive information at the same time. It used a special data transmission technique called packet switching which was later adopted by the internet. By this a computer would send a packet that contained data, destination address information, error detection control information and packet sequencing information

By 1973 e-mail was the most common service on the internet. It was not until 1979 that the media companies connected to the internet. By 1981, the importance of the internet had been shown to many people and thus ARPANET become the backbone on which many organizations started connecting hence its expansion and growth.

Eventually On July 1 1983, this collection of internet-worked networks became known as the INTERNET. By 1987, the internet boasted of 10,000 host computers, however access was largely limited to the United States of America and some nations in Europe. As the internet importance grew, businesses spent a lot of money to improve it as a way of enhancing their services to customers. Also competition


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grow high between software and hardware manufacturers and this led to technological advancements to meet the internet working needs. The result was a great increase in bandwidth (message transmission capacity) and the internet became cheaper.

By 1994 over three million computers were connected to the internet which has grown today and covers the whole world. It is now being used by governments, private organizations and individuals to send and receive messages for conduction of business and all aspects of life.

Uses of the internet

1. The internet helps to link thousands of computers enabling them to share information.

2. It eases access to information.

3. It offers online chatting.

4. The government uses the internet for distribution of information and internal communication.

5. Businesses use the internet to sell and buy products online and interact with other businesses.

6. Education and medical research is available on the internet.

7. It provides employment opportunities.

8. Social networking

Advantages of the internet

1. Enhancement of transport and communication.

2. Helps in accounting and finance.

3. Access to information world wide.

4. Business.

5. E-banking.

6. Climatic and weather forecasting.

7. Entertainment and leisure.


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8. Employment.

9. Security and military.

10. Education and telecommunication.

11. Provide information to others.

Disadvantages of the internet

1. There is no privacy for information.

2. Information control is limited.

3. Installation and maintenance costs are high.

4. Virus threats make data storage insecure.

5. Internet spasm which are irritating.

6. I.T related diseases e.g. eye sight, repetitive strain injury, e.t.c.

7. Moral decay due to pornographic materials. Increased crime through piracy, forgeries and scams.

8. Continued isolation of man.

9. Unemployment as the unskilled get retrenched.

Factors that affect communication over the internet1. Transfer rate: this is the speed of transmitting data and information. Transfer

rates are usually expressed in bits per second (bps), kilobits per second (kbps) or megabits per second (Mbps).

2. Bandwidth: the transfer rate of a transmission medium depends on the medium’s bandwidth. Band width is the rate of data transfer.

3. Network topology; since data travels in both directions in a network, if data collides, then it has to be sent again, and slowdown the network. Star networks have fewer collisions and usually run faster.

4. Capacity of hardware: hubs, switches and network interface cards have their own maximum speeds.


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5. The server: amount of RAM and the speed of the hard disk.

6. Location of software and files: storing software on the workstation hard disk reduces network traffic and speeds up performance.

Requirements for an internet connection1. An ISP to supply the intern

2. et.

3. A Pc (computer with a network card)

4. Network operating system (an operating system)

5. A browser (internet explorer or Netscape navigator)

6. Communication media (physical cables e.g. twisted pair, coaxial cable or wireless communication e.g. wireless antenna, microwave, infra red)

7. Technical know to configure the internet flow in your computer.

TRANSMISSION MEDIAThese are the physical or wireless pathways used to transmit data and information from one point to another. They include telephone lines, radio-waves, microwaves and satellite.

Telecommunication lines connect a computer to the internet using telephone lines and a modem to dial a remote computer.

A modem is a device that connects a computer to a telephone line or cable television network and allows information to be transmitted to or received from another computer. It converts digital signals sent from one computer into analog signals (modulation), which are then transmitted by telephone lines to the receiving modem, which converts the signals back to digital signals that the receiving computer can understand (demodulation). Since dial up connections are slow and unreliable, they are being replaced by dedicated digital leased lines and optical fiber cables.

Satellite transmission helps in data transfer across continents through a wireless uplink channel to the satellite. It then sends the data signal to the base station on another continent where it is picked up and sent to telephone exchanges for transfer to the destination computer.


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Global system for mobiles (GSM) also provides a wireless connectivity to mobile device users known as General Packet Radio Service (GPRS).

INTERNET SERVICE PROVIDER (ISP)An internet service provider is any company that provides internet access to the end users or internet access to customers as a service. This can be daily, monthly, or yearly for a fee. They are called public access networks because they offer services to the general public.

This is a company that sells internet as a service. They supply connections to the internet as well as other services. These are different in most countries but for the case of Uganda, we have Africa online, America online, orange, MTN, UTL, Zain e.t.c

Customers can be businesses, individuals and organizations. A user buys subscription either monthly, quarterly or annually. The ISP gives the user an identification username and password and a phone number. With a computer and a modem, the user calls, connects to and logs onto the service provider’s computer. The user then enjoys services such as WWW, E-mail, FTP, Telnet, web hosting, domain name service and proprietary online services.

Uses of an ISP

1. Most ISPs provide their users with mailbox, which stores their e-mails, on a special server called a mail server.

2. An address that points to a specific resource on the web

3. They operate LANs connected to the World Wide Web.

4. They connect organizations and individuals to the Web.

5. They provide technical support.

Factors to consider when choosing an ISP

1. Bandwidth of the ISP.

2. Nature of customers.

3. Past experience.


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4. Software.

5. Types of connections offered.

6. Administrative support/budget.

7. Consultancy from technical specialists in that field.

THE WEB AND WEB BROWSERSThe World Wide Web (WWW), also called the Web, is a world wide collection of electronic documents. Each of these documents on the web is called a web page.

A Web page is a file of information stored on a web server.

WWW consists of a set of protocols and software that allows the internet to display multimedia documents. It offers resources such as text, photographs, animation, films, and music, video or computer programs. WWW provides a single user interface for accessing its protocols such as FTP, Telnet and Usenet News.

A web site is a collection of related Web pages or related resources located on a web server. It’s an electronic page that has links with other pages and contains information, data e.t.c. OR is a web server in which or where information of a particular organization or company or subject is stored.

A web site always has an entrance page, presenting the site and working as a starting point for navigation around pages on the site. This type of entrance page is called a home page. It’s the starting page or a table of contents for a web site and normally has a name called index.htm or index.html.

A blog is a website that contains personal information which can easily be updated. Some at as resumes, diaries and can also be used for business, advocacy and campaign purposes.

Multimedia sites normally contain photos, movies, music, web TV and internet radio. They are purposely made for entertainment.

Web pages containing text and multimedia elements are created using Web page authorizing software such as Microsoft FrontPage, macromedia Dream weaver, Adobe GoLive and Adobe Page Mill.

A document that contains words or graphics that connect to other documents is called hypertext. These words are called links and are selectable by the user. A single hypertext can contain links to many documents and serve as a link to other


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documents. Web page documents in most cases have links to each other called hyperlinks. The content presented on websites contains hypertext, icons and pictures. By clicking on the hypertext or icons with the mouse, users instruct their browser program to connect to the website specified with the URL contained in the hypertext link.

Hyperlinks on a web page allow a user to

Move to other pages

Store links to your favorite web sites.

Keep a record (history) of websites visited recently.

Navigate back to pages just visited.

Search for web pages

Save and print web pages.

Hypertext is produced by a language known as Hypertext Markup Language (HTML). it is a markup language that describes how a web page should be formatted and displayed in a web browser. This language allows programmers to compose text (also known as ASCII) data, pictures, sound, animations and video for screen display.

It also allows programmers to add attachments to URLs which enable the linking of different Web pages to other pages on the internet. HTML encodes links with their correct URL.

HTML is a collection of platform-independent styles indicated by markup tags. It contains standard codes or tags that determine how a web page looks when displayed.

Hypertext documents usually contain references to other URLs that appear in bold, underlined or colored text. These end with extensions that indicate the type of organization that sponsors the website for example, .gov for government agencies, .edu for academic institutions, .com for commercial enterprises’, .org for non profit organizations, .net for organizations engaged in the maintenance of the internet, e.t.c.

Websites reside on computers called internet servers and when connected to the internet, web browser software communicates with the servers asking them to send a copy of the web page to your computer.


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Every website has a specific address on the WWW called a Uniform Resource Locator (URL). A URL is a unique address of a Web page. It tells the browser where to locate the Web page. A URL consists of a protocol, a domain name, and sometimes the path to a specific Web page or location on a Web page. Examples include;

http://www.usa.edu.pk

First part of a URL specifies the protocol used for connection to the server.

Protocols

- http:// Hypertext Transfer Protocol, for Web sites

- https:// Hypertext Transfer Protocol, secure

- ftp:// File Transfer Protocol

- Localhost:// Information from a local Web server

Domain Name

The next part of the URL specifies the name of the server on which the web resource is held which is Domain Name. It is a string of identifier separated by full stops (called ‘dot’ when you are reading out an address). Identify the type of organization and often the country in which the server is located. People prefer to use names for things.

Domain Name Server (DNS) coverts names to number

International codes include:

.ac an academic institution

.co a company that trades in a single country

.com a commercial organisation that trades internationally

.edu an educational establishment

.gov a government department or other related facility

.nato a NATO installation

.net an organisation or company that provides Internet access

.org a non-commercial organisation, such as a charity


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.tm a trade-marked business name

UK-specific codes include

.ltd a UK Limited company

.sch a school

A 2-character country code may follow – there are hundreds of these including


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au Australia

es Spain

sg Singapore

uk UK

ch Switzerland

Pk Pakistan


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Many factors affect how fast a web page travels from its web site to your computer. These include;

1. Traffic on the internet.

2. The size of the page.

3. The ISP.

4. Web site data transmission.

5. Modem data transmission.

6. Graphics, sound, or videos in addition to text.

BROWSERS

A browser is a software application which enables a computer to locate, download and display documents containing text, sound, video, graphics, animations and photographs located on computer networks. It allows users to access web information by downloading information to a computer through a modem and then displaying it. Commonly used browsers include internet explorer, Mozilla Firefox, Netscape, Google chrome, opera mini, e.t.c.

The act of viewing and moving about between documents on computer network is called surfing or browsing the internet.


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PROTOCOLSA protocol is a set of rules and procedures that govern the exchange of data between two components. They govern how data is sent from one point to another and are designed to specify how computers interact and exchange messages. Both the sender and the receiver must use the same protocol when communicating.

Functions of protocols

Identifying the different devices in the communication path.

Establishing the speed and method to be used for the transmission of data.

Determining how errors are to be detected and corrected.

Altering the receiving device to incoming data and defining the way receipt of data is to be acknowledged by the receiving device.

Types of protocols

1. Transmission control protocol (TCP)

This is a set of rules that allow computers to connect to the internet. It is a collection of rules that govern the way data travels from one computer to another across networks. It involves two separate protocols i.e. TCP which is responsible for breaking up messages into datagrams (packets), reassembling them, resending and putting things back to their right order, and IP which is responsible for routing individual datagrams.

2. File transfer protocol (FTP)

This is an internet standard that allows users to upload and download files with other computers. This protocol enables transferring of text and binary files over TCP connection. It allows transferring files according to a strict mechanism of ownership and access restrictions. Using FTP you can download files from the Web. FTP files have ftp as the first part of the address instead of http.

An FTP server is a computer that allows users to upload and download files using FTP.

An FTP site is a collection of files that reside on an FTP server.

You can also use FTP to upload pages onto a Web site

It is currently the most common way to publish a site because files can easily be uploaded to an FTP server, from the computer where the site was developed.


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You can use specific software such as CuteFTP to do this or some WYSIWYG HTML editors such as Dreaweaver have inbuilt tools which support this.

3. Hypertext transfer protocol (HTTP)

This is a language that web clients and servers use to communicate with each other. It governs the transfer of hypertext between two or more computers across the World Wide Web.

It is thus a client server model making use of the TCP/IP protocol.

Some URL's (uniform resource locator) start https in this instance the s stands for secure, which will allow you to contact another computer, (such as on-line banking) with 128 -bit encryption through a secure port.

4. Point-to-point protocol (PPP)

This provides connections for hosts to networks or between two routers using a security mechanism. It is a known protocol for connections over regular telephone lines using modems on both ends and thus used for connecting personal computers to the internet.

5. Simple mail transfer protocol (SMTP)

This is a set of rules which allow two programs to send and receive mails over the programs.

6. Telnet

This is a terminal emulation protocol that allows a user to log onto a remote device. It is a set of procedures that enable a user of one computer on the internet to log onto other computers on the internet provided the user has a password for the distant computer or the distant computer provides publicly available files. Computers with large electronic databases like library catalogs use telnet to search the databases.

THE E-MAILElectronic mail is the transfer of electronic messages from one geographical location to another using computers and related computerized devices.

Each user of e-mail has a mailbox address to which messages are sent. These messages can reach with in a matter of seconds. It enables the sending of electronic files to a person’s e-mailbox by attaching files.

To receive an e-mail, one has to open up the e-mail service like www.yahoo.com, www.hotmail.com, e.t.c and then sign in with a valid user name and password.


http://www.hotmail.com/

http://www.yahoo.com/

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Email addresses include the @ symbol, such as [email protected].

Emails can be created online (i.e. whilst connected to the Internet – ideal for users who have broadband Internet connection) or offline (i.e. before connecting to the Internet – ideal for users who have expensive dial-up Internet connection).

E-mail messages are not restricted to computers only but to many mobile phones, land lines and personal digital assistants.

Facilities of e-mail

1. Send a message anywhere in the world for the price of a local call;

2. Attach files documents, photographs, maps, programs;

3. Keep an address book of people you regularly e-mail;

4. Send the same letter to a group of people simultaneously;

5. Reply to an e-mail simply by clicking on the reply button;

6. Forward a received message with comments to an individual or group;

7. Pick up your mail from anywhere in the world with special software.

8. Join a mailing list get free information sent to you regularly

Uses of e-mail

1. Communication between businesses.

2. Sending one message to many people.

3. Keeping in touch with friends and family.

4. Attaching files.

Advantages of e-mail

1. It is fast.

2. Ability to send to multiple recipients; the message can be sent simultaneously to a group of people.

3. It is easy to send a reply to an e-mail as soon as it is received using the reply button.


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4. It is inexpensive and easy to send the same e-mail message to different people.

5. There is an assurance of whether the mail has been delivered.

6. Offers free mail like sports which can be subscribed for.

7. It’s universal as one does not need to change addresses where he or she is located.

8. E-mails are quick to write and less formal than letters.

9. It’s ideal to communicate with people over long distances.

10. E-mails are cheaper since they do not involve stamps, envelopes and paper.

11. It is easy to attach a copy of the sender’s e-mail with a reply and this saves them the burden of searching for the original message if need for referring to it arises.

Disadvantages of e-mail

1. Not every one has the equipment to send and receive e-mail.

2. E-mails are not secure because they can be accessed by hackers.

3. They contain junk mail which becomes a problem as it wastes time going through irrelevant information.

4. The equipment used to send and receive e-mails is expensive.

5. It discriminates the illiterate and people who have no access to internet services.

6. It can only be efficient if users frequently check their mail.

Features of an e-mail window

Subject: is the theme of the e-mail message

To: carries the address of the recipient

Cc: enables copies of the e-mail message to be sent to the third party while acknowledging other recipients.

Bcc: enables copies of the e-mail to be sent to a third party without acknowledging any other recipients (if present).


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Newsgroups

These are organized groups of internet users who wish to share ideas and interests. Once joined, one can participate in discussion forums and debates.

A newsgroup is a repository usually within the Usenet system, for messages posted from many users at different locations

Newsgroups are Internet-based discussion groups devoted to discussing specific topics or interests (e.g. rock bands, world politics, hobbies or sports).

Usenet was created in 1979 by a group of American Computer science graduates.

Newsgroups revolve around specific topics, such as wireless technology or organic gardening. You can read what others have written and reply your own thoughts.

These are the bulletin boards of the Internet. There are currently over 5,000 newsgroups. They were originally developed so that scientists could post questions (and answers) to each other to share their knowledge of the bugs.

Newsgroups have also been hit by bulk junk mail messages (known as SPAM) which make certain newsgroups unusable.

Search engines

These are specialized programs that help the user to easily search for information on the internet for example Google, Alta vista, Excite and Yahoo.

Chat

This allows a large number of people to chat amongst themselves in real time from various locations.

Conferencing

This is the dynamic exchange of all kinds of information in a context of structured conversations organized by item and allowing a participant to contribute spontaneous responses to any item in the conversation. Its goal is to structure an online conversation for decision making, technical support, and community building, project management, distance education, electronic meetings and many others.

Each person has a computer linked to the Internet (or telephone system). A camera and microphone are used to input pictures and sound which are then transmitted between the computers. It is possible, with appropriate hardware and an ISDN line

Internet Relay Chat (IRC)


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This is a 'real time' chat system built around internet technology. There are IRC clients available for every operating system.

IRC make use of 'channels' to set up a conversation between two or more people. It is still used today to chat on the internet, but 'Instant Messaging' systems such as MSN and ICQ and AOL have become more popular. IRC are live. Whatever you say on the channel is instantly broadcast to everyone on the same channel.

Chat rooms are pages on a website or online service where users can ‘chat’ with other users. This is done by typing messages that are displayed on the screens of others users who are logged-on to the ‘chat room’. Chat rooms are also called ‘online forums

Telnet

Telnet is a protocol enabling users to manage a remote computer connected to the Internet. Once you have logged on it is as though you were sitting at the keyboard of the remote computer. The telnet console operates in a very similar way to conventional DOS-based window. Computers with large electronic databases like library catalogs use telnet to search the databases. Web servers can be remotely administered by using Telnet.

VIRTUAL NETWORK CONNECTION (VNC)

To remotely administer a server using a GUI environment software such as Virtual Network Connection (VNC) can be used.

For this appropriate client server software would need to be installed, then you can run software on the remote machine as if you were actually sitting at it.

INFORMATION TECHNOLOGYInformation technology (IT) is the use of computers and communication technology to enhance education. It is the use of computing with high speed communication links to spread information from one place to other.

I.T uses all types of equipment or programs that are used in processing information. The World has become a global village and information can be communicated in any shape such as Photographs, Movies, Text, Digital diagrams

Benefits of ICT

1. Computer-assisted instructions (CAI)

Teachers can use computers and other ICT equipment to present teaching materials in a more interesting way.


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2. Computer-assisted learning (CAL)

Students can use computers and appropriate software to answer and learn at their own pace.

3. Computer-assisted assessment (CAA)

Teachers can use computers to mark the answer scripts thereby reducing time and labor.

4. Distance learning through computer-based training and web-based training.

5. Simulations of experiments or real life situations that may be hazardous.

6. Electronic library systems for searching, borrowing and returning books.

7. School administration and management system (SAMS)

Used by schools for keeping of records of students and producing report cards or other related documents.

8. Edutainment

This is a type of education software that combines education with entertainment.

Advantages of using ICT

1. CAI and CAL packages with multimedia effects make learning more interesting and interactive.

2. Teachers can present subject matter and explain abstract concepts clearly with multimedia.

3. Students can work at their own pace, repeating sections they do not understand.

4. Students can learn by them selves when the teacher is not available.

5. Students can easily get their results or feed back immediately after an answer or action.

6. There are rich educational resources on CD-ROMs and the internet.

7. Teachers can show experiments that are difficult to perform or dangerous in nature through simulation software.

8. Advanced instructions can be given to students in areas where the teacher may not be qualified.

9. The material is presented in a consistent way i.e. you are not dependant on the skills of a particular teacher.


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10. Links to other schools or colleges or with industrial or business organizations.

11. Enables use of productivity tools like word processors for use in projects and other school activities.

12. Enhances long distance learning for those unable to attend school or for university students.

13. There are special facilities available for students with disabilities e.g. students with cerebral palsy may control the computer by speaking to it, sighted students may be able to change text size and back ground color, and blind students can use text to speech conversion packages.

14. One package is paid for thus it is cost effective as fewer teachers are required.

15. Computers are endlessly patient.

16. Gives access to the internet and thousands of online databases.

Disadvantages of ICT

1. Face to face interaction between teachers and students may be reduced.

2. Initial investment project is not affordable by schools.

3. Does not benefit the blind and dumb.

4. Makes teachers redundant and students lose social interaction as they become more isolated in their own cyber world.

5. It can be very boring sitting in front of a computer screen.

6. Computers may not motivate students in the same way as a good teacher.

7. Students can only follow what the CAL packages are predefined to offer.

8. There is need for trained staff to run the project.

9. To run this kind of project there has to be power.

10. It only benefits schools which have trained perfectly in English accent since CDs come in American English.


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Advantages of information technology to education

1. Provision and access to important literature on the net.

2. Interactive source of learning.

3. Availability of virtual university.

4. Faster communication with tutors, fellow students e.t.c

5. Integration of computers has enhanced teaching of other subjects using demonstrations and illustrations.

6. Enriched research work by the use of the internet by facilitating data capture.

7. As a subject studied it has offered a new discipline in education i.e. enriched the education curriculum.

8. Provision of edutainment and for entertainment after a long day’s work.

Disadvantages of information technology to education

1. Wastage of study time e.g. doing or engaging in unproductive work.

2. Exposure to illicit material has led students adopt negative behaviors.

3. Over dependence on computers

4. Increased costs of education and learning

5. Learning of computer needs specialized skills which are not readily available to some communities.

6. Information provided on the internet does not provide good education

7. The security of the internet is so relaxed and piracy of people’s work (research) goes inches iced.

FUTURE EVOLUTIONS OF COMPUTER SYSTEMSIt is easy to predict that the computers and related equipment will get faster in memory, smaller and cheaper due to technology advancements and trends recognized and predicted today. Computer technology will find new applications and manufacturers will strive to make computing easier and cheaper. As costs decline, performance and ease of use rises.


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The following are the possible future trends in computer systems:

1. Future computer capabilities They are going to have more powerful, smaller processors and faster access to memory. They will have operating systems that will handle real-time data analysis and object-oriented. They will have improved user interfaces that offer users easier and more intuitive

access to information. They will have multimedia applications that will be fully incorporated into some

information systems because data is easier to interpret when presented as a combination of sight, sound and motion.

2. Physical sizeMost hardware components will get smaller and faster implying that computers will become smaller and do more.

3. PriceAs technology advances, the price of computers will go down. Every sphere of life will be permeated by computers, which will be common even among people of average earning.

4. SoftwareThere will be software developments to allow users easily operate computer systems. The best programming and operating systems are moving towards object-orienting systems to facilitate documentation.New OS will focus on object linking message passing and data sharing. There will also be use of very very high languages.

5. Artificial intelligence.Artificial intelligence is the process of building computer systems that simulate human thought processes and actions. Its goal is not to replace human intelligence rather to help people to be more productive.It attempts to develop computer systems that can mimic or simulate human thought processes and actions including reasoning and learning from past actions.Although it has not been yet possible, several tools that emulate human problem solving and information processing have been developed such as expert systems, natural language processing, artificial neural networks and robots.

6. Cyber world dependency on the internet.7. There will be need for more computer skills.

Expert systems


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These are computer programs that essentially emulate the knowledge of human experts skilled in particular fields for example of a geologist or a medical doctor. They have both textbook knowledge and tricks of trade that an expert acquires after years of experience.Expert systems are applied in: Finance/business planning Teaching field i.e. they compliment teacher’s knowledge e.g. typing tutor Project planning monitoring

Natural language processingThis is the capacity of computers to understand human language and translate it into actions upon which to act. For example you could create a list of students from a data base by typing “print a list of students with outstanding balance of greater than 100,000”. It is expected that in future, language processing software will understand language from any speaker and translate it into any other language upon which to act.

Artificial neural networksComputers will have a scheme resembling those in human brain and nervous systems. Data will be transmitted to and from the processor at many times the speed of the old arrangements. It is expected to help in image recognition, handwriting and speech recognition.The old arrangement is known as the Von Neumann architecture after its originator John Von Neumann. The processor and the main memory are physically separated although joined by communication links. Present computers and super computers are thus relatively slow because of the built-in structural limitations. The processor spends most of its time waiting for data to come from or go to memory.

RobotsThis is a field of study concerned with developing and building robots. They are machines that are used in factories and can be reprogrammed to do more than one task.They are sued in the manufacturing industry mainly to reduce costs and increase productivity.They are excellent in executing repetitive tasks that human beings find boring.They do not get tired and are ideal to replace human beings on hazardous jobs.Robots are of different types which include industrial, perception and mobile robots.1. Industrial robots are used in factories to perform certain assembly tasks e.g. machines

used in automobile plants to do welding, painting, loading and unloading; in garment industry robots pattern, cut and create pieces of fabrics for clothing.

2. Perception robots imitate human senses e.g. a robot with television camera or vision system can be used for guiding machines, tools for inspecting products and for identifying and sorting parts. Other types rely on the sense of touch e.g. those used on microcomputer assembly lines to put parts into place.


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3. Mobile robots act as transporters e.g. mail mobiles which carry mail to offices following a pre-determined route.

SimulationsA simulation is a software package that recreates or simulates a complex phenomena, environment, or experience in order to provide the user with a better understanding.A simulation is interactive, and relies upon decisions made by the user, often in ‘real time’. Simulation uses computer modelling in order to work. The difference between a model and a simulation is that a simulation also uses something physical to mimic the system. Examples of simulations Thrill ride simulator somewhere like Disneyland. Another form of simulation is Virtual Reality. Experiments in chemistry Airline training Traffic lights Systems Nuclear physics experimentsCommon uses of simulations include: Computer games. Flight simulators. Economic models. 3D Engineering simulations.

Roles of computers in the future

1. In business: used in high tech management, information systems and transactions.2. In communication: very fast and reliable systems3. In education: virtual universities, electronic publications, very fast access to any

topic/subject4. In security: high tech security systems by providing efficient and effective protection,

computer guided warfare.5. In industry: high tech manufacturing systems, increased use of robots, computer aided

designs in manufacturing6. In homes: involvement of computers in domestic work i.e. interior and exterior designs,

making home schedule7. In research: data capture, storage, manipulation through high involvement of computers.8. Creation of virtual world e.g. “7 continent” where everything is computerized (all

aspects of life)

IMPACT OF COMPUTERS IN OUR SOCIETY TODAYHuman issues


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1. A large proportion of the manufacturing and assembly works is now done by robots.2. Managers rarely have shorthand secretaries but are expected to work process their own

letters.3. Bank notes are rarely hand counted but are either weighed or counted using machines.4. Shop assistants no longer need to calculate the change that should be given since the

checkout computers do that.5. Payrolls are now automatically done using application programs.

Work skills and retraining

1. Jobs have been created that require new ICT skills although a number of work skills are no longer required. These include programming, network installation, network administration, web design e.t.c

2. As a result of de-skilling and re-skilling, training on a large scale is required since not many people can be employed. Re-training of staff is done to fulfill the changing job requirements which have created a new industry of people responsible for training the work force for the information age. These include health care, commerce and industry, communication, broadband, web TV and radio.

3. In the future, evolution of computer architecture will be the trend in smaller, faster and with large storage such as bus development, compact pc, card bus, fiber channels, processor development, super scale CPUs, simultaneous multithread processor (SMP), chip microprocessor (CMP), intelligent RAM (IRAM).

4. Artificial intelligence.

Harmful effects

1. Computer crimes2. Data protection and legislation3. Computer ethics4. Information policy5. ICT legislation (data, computer misuse, health safety)6. Obscene publication.7. Moral degeneration.8. Quire morals like lesbians, cults, hackers9. Affect sight10. Consume a lot of power11. Training and repair is very expensive and experts are few12. Internet can spread viruses to millions of computers in seconds.13. Hackers can easily access and corrupt data records.


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CAREER OPPORTUNITIES IN THE COMPUTER FIELDAny organization of any size needs information processing. This is done by a separate IT department usually responsible for dealing with the IT related issues or it may be an outside source.

These responsibilities include:

1. IT procurement (hardware, software, networking)2. Installation and maintenance of IT equipment.3. Network installation and maintenance.4. Identification of user requirements (system analysis)5. Data base administration (data base backup, performance, tuning e.t.c)6. Website design, development and maintenance.7. IT training.

There are software houses that specialize in developing software applications. These would have teams of analysts, software engineers, programmers, computer technicians, computer operators, system testers, e.t.c


Documents

· Web viewCOMPUTER STUDIES. [email protected], TEL;+256758-183719. COMPUTER STUDIES CURRICULUM SEQUENCE. SENIOR 1 Term 1 …