FUNDAMENTALS OF COMPUTERS AND INFORMATION … · NCEC INSTITUTE OF SCIENCE & TECHNOLOGY, BHOPAL, 9893803508 8 Disadvantages of Computers 1. No I.Q • A computer is a machine that

NCEC INSTITUTE OF SCIENCE & TECHNOLOGY, BHOPAL, 99893803508, 7771013508

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FUNDAMENTALS OF COMPUTERS AND INFORMATION TECHNOLOGY

Unit -I

Computer system concepts, Application area, advantage & disadvantage, components of a computer system – control unit, ALU,

input/output, memory, mother Board, Generations of computers, Configurations of computer system, types of PCs- desktop,

laptop, Notebook, palmtop, PDA, Special purpose computers, Supercomputers Characteristics And area of Uses, Primary Vs

Secondary Memory, RAM, ROM, EPROM, PROM.

Various Storage Devices- Magnetic Disks, Hard Disk Drives, Floppy, Disks, Zip Drive, optical Disks, CD, VCD, CD-R, CDRW,

DVD, DVD-RW, Blue Ray Disc, flash drives SD/MMC Memory cards, solid- State Drive(SSD).

Unit – II

Input Device: keyboard, Mouse, Trackball, Joystick, Scanners, Digitizing tablet, Digital camera, MICR, OCR, OMR, light pen,

Barcode & Barcode Reader, Quick Response Code (QR code), Voice Recognition, Touch Screen.

Output Devices: Monitors- Characteristics and types of monitor, size, Digital, Analog, Resolution, Refresh Rate, Interlaced/Non-

Interlaced, Dot pitch, Video Standard-VGA, SVGA, XFA etc. Printers and its Types impact and Non-impact printer, Dot Matrix,

inkjet, laser, plotter, 3D printers, Sound Card and Speakers.

Unit – III

Software and its Need, Types of Software-System software, Application Software, System Software- Operation System –

definition & function, Device Drivers & Utility programs, Introduction & Features of DOS, Windows, Programming Languages-

Machine, Assembly, High level, 4GL, their merits and Demerits, Uses of Assemblers, Compilers and Interpreter.

Application Software and its Types- word processing, Spreadsheet, presentation Graphics, Data Base Management, Desktop

publishing, communication, Educational, Graphics & Multimedia, Business Accounting, MIS, Gaming and ERP Software etc.

Computer coding system– ASCII, ISCII and Unicode, Number system of computer, Binary, Octal, Decimal, Hexadecimal their

conversion.

Unit – IV

Use of communication and IT, Communication process, component of communication- , receiver Transmission medium &

protocol, Communication types- Simplex, Half Duplex, full Duplex, Communication Channels-Twisted, Coaxial, Fiber Optic,

Modem- working and characteristics. Types of network- client/server and peer-to-peer networks, Types of connections- Dialup,

Leased Lines, ISDN, DSL, RF, Broad band uses, advantages & disadvantages.

Types of Network- LAN, WAN, MAN, internet, VPN etc., Topology of LAN- Ring, Bus, Star, Mesh and Tree topologies-

structure, uses, advantages & Disadvantages, Components of LAN- Media, NIC, NOS, Network devices – Bridges, HUB, Routers,

Repeater, Gateways uses, advantages & Disadvantages.

Unit – V

Disk Operating System (DOS): introduction, DOS Basics – Drive Name, FAT, File and Directory Structure and naming Rules,

booting process, DOS System files.

DOS Commands: internal – DIR, MD, CD RD, COPY CON, DEL, REN External- TREE, EORMAT, SOFT, FDISK, MODE,

ATTIRIB, HELP, SYS etc., Concepts of Free/Open Source and proprietary Software, applications and use of computer in various

fields.

LINUX: History & Features, Hardware Requirements of Linux, Various flavors of Linux, Linux Standard Directories, Functions

of profile and Login Files in Linux, Linux Kernel, Login and Logout from Linux from Linux System, Linux Commands- BC,

CAL, CAT, CD, CLEAR, CMP, CP, MV, DATA, FIND, IS, PWD, MKDIR, MORE, RM, RMDIR, CHGRP, CHMOD, WHO,

WHOIS.


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UNIT-1

COMPUTER:

Computer is an advanced electronic device that takes raw data as an input from the user and

processes it under the control of a set of instructions (called program), produces a result

(output), and saves it for future use. A computer is an electronic data processing device, which

accepts and stores data input, processes the data input, and generates the output in a required

format.

COMPUTER SYSTEM CONCEPTS: A computer is more than a high-powered collection of electronic devices performing a variety

of information processing chores. A computer is a system, an interrelated combination of

components that performs the basic system functions of input, processing, output, storage,

and control, thus providing end users with a powerful information processing tool.

Understanding the computer as a computer system is vital to the effective use and

management of computers.

A computer is system of hardware devices organized according to the following system

functions.

• Input. The input devices of a computer system include keyboards, touch screens, pens,

electronic mice, optical scanners, and so on.

• Processing. The central processing unit (CPU) is the main processing component of a

computer system. (In microcomputers, it is the main microprocessor.) In particular, the

electronic circuits of the arithmetic-logic unit one of the CPU’s major components,

perform the arithmetic and logic functions required in computer processing.

• Output. The output devices of a computer system include video display units, printers,

audio response units, and so on, they convert electronic information produced by the

computer system into human intelligible form for presentation to end users.

• Storage. The storage function of a computer system takes place in the storage circuits of

the computer’s primary storage unit, or memory, and in secondary storage devices such as

magnetic disk and tape units. These devices store data and program instructions needed

for processing.

• Control. The control unit of the CPU is the control component of a computer system. Its

circuits interpret computer program instructions and transmit directions to the other

components of the computer system.


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APPLICATION AREA OF COMPUTER:

1. BUSINESS:

A computer has high speed of calculation, diligence, accuracy, reliability, or versatility

which has made it an integrated part in all business organizations.

Computer is used in business organizations for −

• Payroll calculations

• Budgeting

• Sales analysis

• Financial forecasting Managing employee database Maintenance of

stocks, etc.

2. BANKING:

Today, banking is almost totally dependent on computers. Banks provide the following

facilities -

• Online accounting facility, which includes checking current balance, making

deposits and overdrafts, checking interest charges, shares, and trustee records.

• ATM machines which are completely

automated are making it even easier for customers to deal with banks.

3. INSURANCE: Insurance companies are keeping all records up-to-date with the help of computers.

Insurance companies, finance houses, and stock broking firms are widely using computers

for their concerns.

Insurance companies are maintaining a database of all clients with information showing −

• Procedure to continue with policies

• Starting date of the policies

• Next due installment of a policy

• Maturity date

• Interests due

• Survival benefits

• Bonus

4. EDUCATION:

The computer helps in providing a lot of facilities in the education system.


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• The computer provides a tool in the education system known as CBE

(Computer Based Education).

• CBE involves control, delivery, and evaluation of learning.

• Computer education is rapidly increasing the graph of number of computer

students.

• There are a number of methods in which educational institutions can use a

computer to educate the students.

• It is used to prepare a database about performance of a student and analysis is

carried out on this basis.

5. MARKETING:

In marketing, uses of the computer are following −

• Advertising − With computers, advertising professionals create art and

graphics, write and revise copy, and print and disseminate ads with the goal of

selling more products. • Home Shopping − Home shopping has been made possible through the use of

computerized catalogues that provide access to product information and permit

direct entry of orders to be filled by the customers.

6. HEALTHCARE:

Computers have become an important part in hospitals, labs, and dispensaries. They are

being used in hospitals to keep the record of patients and medicines. It is also used in

scanning and diagnosing different diseases. ECG, EEG, ultrasounds and CT scans, etc. are

also done by computerized machines. Following are some major fields of health care in

which computers are used.

• Diagnostic System − Computers are used to collect data and identify the cause

of illness.

• Lab-diagnostic System − All tests can be done and the reports are prepared by

computer.

• Patient Monitoring System − These are used to check the patient's signs for

abnormality such as in Cardiac Arrest, ECG, etc.

• Pharma Information System − Computer is used to check drug labels, expiry

dates, harmful side effects, etc.

• Surgery − Nowadays, computers are also used in performing surgery.


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7. ENGINEERINGDESIGN:

Computers are widely used for engineering purpose. One of the major areas is CAD

(Computer Aided Design) that provides creation and modification of images. Some of the

fields are −

• Structural Engineering − Requires stress and strain analysis for design of ships,

buildings, budgets, airplanes, etc.

• Industrial Engineering − Computers deal with design,

implementation, and improvement of integrated systems of

people, materials, and equipment.

• Architectural Engineering − Computers help in planning towns, designing

buildings, determining a range of buildings on a site using both 2D and 3D

drawings.

8. MILITARY

Computers are largely used in defense. Modern tanks, missiles, weapons, etc. Military

also employs computerized control systems. Some military areas where a computer has

been used are − Missile Control

• Military Communication

• Military Operation and Planning

• Smart Weapons

9. COMMUNICATION:

Communication is a way to convey a message, an idea, a picture, or speech that is

received and understood clearly and correctly by the person for whom it is meant. Some

main areas in this category are – E-mail

• Chatting

• Usenet

• FTP

• Telnet

• Video-conferencing


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10. GOVERNMENT:

Computers play an important role in government services. Some major fields in this

category are

• Budgets

• Sales tax department

• Income tax department

• Computation of male/female ratio

• Computerization of voters lists

• Computerization of PAN card

• Weather forecasting

ADVANTAGES OF COMPUTERS:

1. High Speed

• Computer is a very fast device.

• It is capable of performing calculation of very large amount of data.

• The computer has units of speed in microsecond, nanosecond, and even the picosecond.

• It can perform millions of calculations in a few seconds as compared to man who will

spend many months for doing the same task.

2. Accuracy

• In addition to being very fast, computers are very accurate.

• The calculations are 100% error free.

• Computers perform all jobs with 100% accuracy provided that correct input has been

given.

3. Storage Capability

• Memory is a very important characteristic of computers.

• A computer has much more storage capacity than human beings.

• It can store large amount of data.

• It can store any type of data such as images, videos, text, audio and many others.

NCEC INSTITUTE OF SCIENCE & TECHNOLOGY, BHOPAL, 9893803508

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4. Diligence

• Unlike human beings, a computer is free from monotony, tiredness and lack of

concentration.

• It can work continuously without any error and boredom.

• It can do repeated work with same speed and accuracy.

5. Versatility

• A computer is a very versatile machine.

• A computer is very flexible in performing the jobs to be done.

• This machine can be used to solve the problems related to various fields.

• At one instance, it may be solving a complex scientific problem and the very next moment

it may be playing a card game.

6. Reliability

• A computer is a reliable machine.

• Modern electronic components have long lives.

• Computers are designed to make maintenance easy.

7. Automation

• Computer is an automatic machine.

• Automation means ability to perform the given task automatically.

• Once a program is given to computer i.e., stored in computer memory, the program and

instruction can control the program execution without human interaction.

8. Reduction in Paper Work

• The use of computers for data processing in an organization leads to reduction in paper

work and results in speeding up a process.

• As data in electronic files can be retrieved as and when required, the problem of

maintenance of large number of paper files gets reduced.

9. Reduction in Cost

• Though the initial investment for installing a computer is high but it substantially reduces

the cost of each of its transaction.


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Disadvantages of Computers

1. No I.Q

• A computer is a machine that has no intelligence to perform any task.

• Each instruction has to be given to computer.

• A computer cannot take any decision on its own.

2. Dependency

• It functions as per a user’s instruction, so it is fully dependent on human being

3. Environment

• The operating environment of computer should be dust free and suitable.

4. No Feeling

• Computers have no feelings or emotions.

• It cannot make judgment based on feeling, taste, experience, and knowledge unlike a

human being.

5. Virus and hacking attacks

• Virus is a worm and hacking is simply an unauthorized access over computer for some

illicit purpose.

• Virus is being transferred from email attachment, viewing an infected website

advertisement, through removable device like USB etc. once virus is transferred in host

computer it can infect file, overwrite the file etc.

6. Online Cyber Crimes

• Online cyber-crime means computer and network may have used in order to commit

crime.

• Cyber stalking and Identity theft are the points which comes under online cyber-crimes.


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COMPONENTS OF COMPUTER SYSTEM

1. Control Unit:

A control unit (CU) (or controller, same thing) is a piece of hardware that manages

the activities of peripherals (separate devices attached to the computer, such as

monitors, hard drives, printers, etc.) Control units found on personal computers are

usually contained on a single printed circuit board.

The control unit fetches one or more new instructions from memory (or an instruction

cache), decodes them and dispatches them to the appropriate functional units to be

executed. The control unit is also responsible for setting the latches in various data paths

that ensure that the instructions are performed on the correct operand values stored in

the registers.

Functions of control Unit:

• Regulate transfers of information between memory and I/O.

• Fetches and decodes instructions from micro programs.

• Responsible for correct instruction execution between a processor's many sub-units.

• Control unit converts received information into sequence of control signals, and

transfer to computer processor.

• It controls data flow inside the computer processor.


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2. ALU (Arithmetic Logic Unit):

An arithmetic logic unit (ALU) is a digital circuit used to perform arithmetic and logic

operations. It represents the fundamental building block of the central processing unit

(CPU) of a computer. Modern CPUs contain very powerful and complex ALUs. In

addition to ALUs, modern CPUs contain a control unit (CU). Most of the operations of a CPU are performed by one or more ALUs, which load data

from input registers. A register is a small amount of storage available as part of a CPU.

The control unit tells the ALU what operation to perform on that data, and the ALU stores

the result in an output register. The control unit moves the data between these registers, the

ALU, and memory.

This unit consists of two subsections namely,

Arithmetic Section

Function of arithmetic section is to perform arithmetic operations like addition,

subtraction, multiplication, and division. All complex operations are done by making

repetitive use of the above operations. Logic Section

Function of logic section is to perform logic operations such as comparing, selecting,

matching, and merging of data.

3. INPUT/OUTPUT DEVICE:

In computing, input/output or I/O (or, informally, io or IO) is the communication between

an information processing system, such as a computer, and the outside world, possibly a

human or another information processing system. Inputs are the signals or data received

by the system and outputs are the signals or data sent from it. The term can also be used

as part of an action; to "perform I/O" is to perform an input or output operation.

I/O devices are the pieces of hardware used by a human (or other system) to communicate

with a computer. For instance, a keyboard or computer mouse is an input device for a

computer, while monitors and printers are output devices. Devices for communication

between computers, such as modems and network cards, typically perform both input and

output operations.

4. COMPUTERMEMORY:

Memory is storage part in computer. It is store the data, information, programs during

processing in computer. It stores data either temporarily or permanent basis.


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5. COMPUTER MOTHERBOARD:

The motherboard serves as a single platform to connect all of the parts of a computer

together. It connects the CPU, memory, hard drives, optical drives, video card, sound card,

and other ports and expansion cards directly or via cables. It can be considered as the

backbone of a computer.

Features of Motherboard

A motherboard comes with following features −

• Motherboard varies greatly in supporting various types of components.

• Motherboard supports a single type of CPU and few types of memories.

• Video cards, hard disks, sound cards have to be compatible with the motherboard to

function properly.

• Motherboards, cases, and power supplies must be compatible to work properly

together.

Popular Manufacturers:-

Following are the popular manufacturers of the motherboard.

• Intel

• ASUS

• AOpen ABIT

• Biostar

• Gigabyte

• MSI

GENERATIONS OF COMPUTERS

1. First Generation:

a. The period 1940 to 1956, roughly considered as the First Generation of

Computer.

b. The first generation computers were developed by using vacuum tube or

thermionic valve machine.

c. The input of this system was based on punched cards and paper tape; however,

the output was displayed on printouts.


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d. The first generation computers worked on binary-coded concept (i.e., language

of 0-1). Examples: ENIAC, EDVAC, UNIVAC, IBM-701, IBM-650.

Advantages:

i. It made use of vacuum tubes which are the only electronic component

available during those days.

ii. These computers could calculate in milliseconds.

Disadvantages:

i. These were very big in size, weight was about 30 tones.

ii. These computers were based on vacuum tubes. iii. These computers were

very costly. iv. It could store only a small amount of information due to the

presence of magnetic drums.

v. As the invention of first generation computers involves vacuum tubes, so

another disadvantage of these computers was, vacuum tubes require a large

cooling system.

vi. Very less work efficiency. vii. Limited programming capabilities and

punch cards were used to take inputs. viii. Large amount of energy

consumption.

ix. Not reliable and constant maintenance is required.

2. Second Generation:

a. The period 1956 to 1963 is roughly considered as the period of second generation of

computers.

b. The second generation computers were developed by using transistor technology.

c. In comparison to the first generation, the size of second generation was smaller.

d. In comparison to computers of the first generation, the computing time taken by the

computers of the second generation was lesser.

e. Some examples are Honeywell 400, IBM 7094, CDC 1604, CDC 3600, and

UNIVAC 1108.


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Advantages:

i. Due to the presence of transistors instead of vacuum tubes, the size of

electron component decreased. This resulted in reducing the size of a computer as

compared to first generation computers. ii. Less energy and not produce as much

heat as the first generation. iii. Assembly language and punch cards were used for

input. iv. Low cost than first generation computers.

v. Better speed, calculate data in microseconds.

vi. Better portability as compared to first generation.

Disadvantages:

i. A cooling system was required.

ii. Constant maintenance was required.

iii. Only used for specific purposes.

3. Third Generation:

a. The period 1963 to 1971 is roughly considered as the period of Third Generation of

computers.

b. The third generation computers were developed by using the Integrated Circuit (IC)

technology.

c. In comparison to the computers of the second generation, the size of the computers

of the third generation was smaller.

d. In comparison to the computers of the second generation, the computing time taken

by the computers of the third generation was lesser.

e. The third generation computer consumed less power and also generated less heat.

f. The maintenance cost of the computers in the third generation was also low.

g. The computer system of the computers of the third generation was easier for

commercial use.

h. Few Examples are: PDP-8, PDP-11, ICL 2900, IBM 360, and IBM 370

Advantages:

i. These computers were cheaper as compared to second-generation computers.

ii. They were fast and reliable. iii. Use of IC in the computer provides the small size of the computer. iv. IC not

only reduce the size of the computer but it also improves the performance of

the computer as compared to previous computers.


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v. This generation of computers has big storage capacity.

vi. Instead of punch cards, mouse and keyboard are used for input.

vii. They used an operating system for better resource management and used the

concept of time-sharing and multiple programming.

viii. These computers reduce the computational time from microseconds to

nanoseconds.

Disadvantages:

i. IC chips are difficult to maintain. ii. The highly sophisticated technology

required for the manufacturing of IC chips.

iii. Air conditioning is required.

4. Fourth Generation:

a. The period 1972 to 2010 is roughly considered as the fourth generation of

computers.

b. The fourth generation computers were developed by using microprocessor

technology.

c. By coming to fourth generation, computer became very small in size, it became

portable.

d. The machine of fourth generation started generating very low amount of heat.

e. It is much faster and accuracy became more reliable.

f. The production cost reduced to very low in comparison to the previous

generation.

g. It became available for the common people as well.

h. Few Examples are: IBM 4341, DEC 10, STAR 1000, PUP 11

Advantages: i. Fastest in computation and size get reduced as compared to the previous

generation of computer.

ii. Heat generated is negligible.

iii. Small in size as compared to previous generation computers.

iv. Less maintenance is required.


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v. All types of high-level language can be used in this type of computers.

Disadvantages: i. The Microprocessor design and fabrication are very complex.

ii. Air conditioning is required in many cases due to the presence of ICs.

iii. Advance technology is required to make the ICs.

5. Fifth Generation:

a. The period 2010 to till date and beyond, roughly considered as the period of

fifth generation of computers.

b. By the time, the computer generation was being categorized on the basis of

hardware only, but the fifth generation technology also included software.

c. The computers of the fifth generation had high capability and large memory

capacity.

d. Working with computers of this generation was fast and multiple tasks could

be performed simultaneously. e. Some of the popular advanced technologies of the fifth generation include

Artificial intelligence, Quantum computation, Nanotechnology, Parallel

processing, etc.

f. Few Examples are: Desktop, Laptop, NoteBook, UltraBook, and

Chromebook.

Advantages:

i. It is more reliable and works faster.

ii. It is available in different sizes and unique features.

iii. It provides computers with more user-friendly interfaces with multimedia

features.

Disadvantages:

i. They need very low-level languages.

ii. They may make the human brains dull and doomed.

TYPES OF PCs:


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The personal computer (PC) defines a computer designed for general use by a single

person. While a Mac is a PC, most people relate the term with systems that run the

Windows operating system. PCs were first known as microcomputers because they

were a complete computer but built on a smaller scale than the huge systems in use by

most businesses.

1. Desktop:- A PC that is not designed for portability is a desktop computer. The expectations with

desktop systems are that you will set the computer up in a permanent location.

Most desktops offer more power, storage and versatility for less cost than their

portable brethren.

2. Laptop:- Laptops are portable computers that integrate the display, keyboard, a pointing device

or trackball, processor, memory and hard drive all in a battery-operated package

slightly larger than an average hardcover book.

3. Notebook:- A notebook computer is a battery- or AC-powered personal computer generally smaller

than a briefcase that can easily be transported and conveniently used in temporary spaces

such as on airplanes, in libraries, temporary offices, and at meetings. A notebook

computer, sometimes called a laptop computer, typically weighs less than 5 pounds and

is 3 inches or less in thickness.

4. Palmtop:- A palmtop is a small computer that will literally fit in your

palm of your hand. Compared to full-size computers,

palmtops are severely limited, but they are practical for

certain functions such as phone books, calendars and email.

Some also have word processors. Spreadsheets etc.

5. PDA:-

• Personal digital assistant is a term for a small, mobile, handheld device that provides

computing and information storage and retrieval capabilities for personal or business

use, often for keeping schedules, calendars and address book information handy.


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• Popular in the 1990s and early 2000s, personal digital assistants (PDAs) were the

precursors to Smartphone. Most PDAs had a small physical keyboard, and some had an

electronically sensitive pad on which handwriting could be received. Original uses for a

personal digital assistant included schedule and address book storage and retrieval and

note-entering. However, many types of applications were written for PDAs.

6. Special-Purpose Digital Computer:- Special-Purpose Computer are designed to be task specific and most of the

times their job is to solve one particular problem. They are also known as

dedicated computers, because they are dedicated to perform a single task

over and over again. Such a computer system would be useful in playing

graphic intensive Video Games, traffic lights control

system, navigational system in an aircraft, weather forecasting, satellite

launch / tracking, oil exploration, and in automotive industries, keeping

time in a digital watch, or Robot helicopter.

SUPERCOMPUTER

A supercomputer is a computer with a high level of performance compared to a general-

purpose computer. Performance of a supercomputer is measured in floatingpoint

operations per second (FLOPS) instead of million instructions per second (MIPS). As of

2017, there are supercomputers which can perform up to nearly a hundred quadrillion

FLOPS. As of November 2017, all of the world's fastest 500 supercomputers run Linux-

based operating systems.

Supercomputers are primarily are designed to be used in enterprises and organizations

that require massive computing power. A supercomputer incorporates architectural and

operational principles from parallel and grid processing, where a process is

simultaneously executed on thousands of processors or is distributed among them.

Although supercomputers houses thousands of processors and require substantial floor

space, they contain most of the key components of a typical computer, including a

processor(s), peripheral devices, connectors, an operating system and applications. As

of 2013, IBM Sequoia is the fastest supercomputer to date. It has more than 98,000

processors that allow it to process at a speed of 16,000 trillion calculations per second.

Characteristics of Supercomputer

• They can support more than a hundred users at a time.


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• These machines are capable of handling the massive amount of calculations that

are beyond the human capabilities, i.e., the human is unable to solve such

extensive calculations.

• Many individuals can access supercomputers at the same time.

• These are the most expensive computers that can ever be made.

• They are used for highly calculation-intensive tasks such as problems involving

quantum physics, weather forecasting, climate research, molecular modeling, and

physical simulations.

• A particular class of problems, known as Grand Challenge problems, is problems

whose full solution requires semi-infinite computing resources.

Uses of a Supercomputer

1. Weather Forecasting:-Your local weatherman bases his forecasts on data

supplied by supercomputers run by NOAA, or the National Oceanic and

Atmospheric Administration. NOAA's systems perform database operations,

mathematical and statistical calculations on huge amounts of data gathered

from across the nation and around the world. The processing power of

supercomputers help climatologists predict, not only the likelihoodof rain in

your neighborhood, but also the paths of hurricanes and the probability of

tornado strikes.

2. Scientific Research:-Like the weather, scientific research depends upon the

number-crunching ability of supercomputers. For example, astronomers at

NASA analyze data streaming from satellites orbiting earth, ground-based

optical and radio telescopes and probes exploring the solar system.

3. Intelligence Agencies:-National Security Agency and similar government

intelligence agencies all over the world use supercomputers to monitor

communications between private citizens, or from suspected terrorist

organizations and potentially hostile governments. The NSA needs the

numerical processing power of supercomputers to keep ahead of increasingly

sophisticated encryption of Internet, cell phone, email and satellite

transmissions -- as well as old-fashioned radio communications. In addition,

the NSA uses supercomputers to find patterns in both written and spoken

communication that might alert officials to potential threats or suspicious

activity.


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4. Data Mining:-Some supercomputers are needed to extract information from

raw data gathered from data farms on the ground or in the cloud. For example,

businesses can analyze data collected from their cash registers to help control

inventory or spot market trends. Life Insurance companies use

supercomputers to minimize their actuarial risks. Likewise, companies that

provide health insurance reduce costs and customer premiums by using

supercomputers to statistically analyze the benefits of different treatment

options.

COMPUTER MEMORY:

Memory is storage part in computer. It is store the data, information, programs during

processing in computer. It stores data either temporarily or permanent basis. Memory

used to important role in saving and retrieving data.

Types of Memory– Mainly computer have two types memory

1. Primary Memory / Volatile Memory. 2. Secondary Memory / Non Volatile Memory.

I. Primary Memory / Volatile Memory– Primary memory is internal memory of the

computer. It is also known as main memory and Temporary memory .Primary

Memory holds the data and instruction on which computer is currently working.

Primary Memory is nature volatile. It means when power is switched off it lost all

data.

Types of Primary Memory– Primary memory is generally of two types.

a. RAM (Random Access Memory) – It stands for Random Access

Memory. RAM is known as read /writes memory. It generally refereed as

main memory of the computer system. It is a temporary memory. The

information stored in this memory is lost as the power supply to the


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computer is switched off. That’s why RAM is also called “Volatile

Memory”

Types of RAM– RAM is also of two types:

i. Static RAM- Static RAM also known as SRAM, retain stored

information as long as the power supply is ON. SRAM are of higher

coast and consume more power .They have higher speed than

Dynamic RAM ii. Dynamic RAM– Dynamic RAM also known as

DRAM, its stored information in a very short time (a few milliseconds)

even though the power supply is ON. The Dynamic RAM are cheaper and

moderate speed and also they consume less power.

b. ROM (Read Only Memory) – It stands for Read Only Memory. ROM is

a Permanent Type memory. Its content are not lost when power supply is

switched off. Content of ROM is decided by the computer manufacturer

and permanently stored at the time of manufacturing. ROM cannot be

overwritten by the computer. It is also called “Non-Volatile Memory”.

Type of ROM: ROM memory is three types names are following-

i. PROM (Programmable Read Only Memory)-PROM chip is

programmable ROM. It is PROM chips to write data once and read

many. Once chip has been programmed, the recorded information

cannot be changed. PROM is also nonvolatile memory.

ii. EPROM (Erasable Programmable Read Only Memory) EPROM

chip can be programmed time and again by erasing the information

stored earlier in it. Information stored in EPROM exposing the chip

for some time ultraviolet light.

iii. EEPROM (Electrically Erasable Programmable Read Only

Memory)-The EEPROM is programmed and erased by special

electrical waves in millisecond. A single byte of a data or the entire

contents of device can be erased.

II. Secondary Memory / Non Volatile Memory– Secondary Memory is external memory

of the computer. It is also known as Auxiliary memory and permanent memory. It is

used to store the different programs and the information permanently. Secondary

Memory is nature nonvolatile. It means data is stored permanently even if power is

switched off.


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The secondary storage devices are:

1. Floppy Disks

2. Magnetic (Hard) Disk

3. Magnetic Tapes

4. Pen Drive

5. Winchester Disk

6. Optical Disk(CD,DVD)

Various Storage Devices:-

1. Magnetic Disks: - A magnetic disk is a storage device that uses a magnetization process

to write, rewrite and access data. It is covered with a magnetic coating and stores data

in the form of tracks, spots and sectors. Hard disks, zip disks and floppy disks are

common examples of magnetic disks.

2. Hard Disk Drive (HDD): - A hard disk drive (HDD) is a nonvolatile computer storage

device containing magnetic disks or platters rotating at high speeds. It is a secondary

storage device used to store data permanently, random access memory (RAM) being

the primary memory device. Non-volatile means data is retained when the computer is

turned off. A hard disk drive is also known as a hard drive.

3. Floppy Disk Drive (FDD): - A floppy disk drive (FDD), or floppy drive, is a hardware

device that reads data storage information. It was invented in 1967 by a team at IBM

and was one of the first types of hardware storage that could read/write a portable

device. FDDs are used for reading and writing on removable floppy discs. Floppy disks

are now outdated, and have been replaced by other storage devices such as USB and

network file transfer.

4. Zip Drive: - A Zip drive is a medium-capacity and portable magnetic disk storage

system launched by Iomega in the mid-1990s. It was popular at the time of launch as

cost per storage unit was lower than that of hard disks, and it could store a larger

amount of data than a floppy disk. The Zip drive was capable of fast data transfer and

was durable and reliable.

5. Optical Disk: - An optical disk is any computer disk that uses optical storage techniques

and technology to read and write data. It is a computer storage disk that stores data


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digitally and uses laser beams (transmitted from a laser head mounted on an optical

disk drive) to read and write data.

6. CD: - CD, a compact disc is a polycarbonate with one or more metal layers capable of

storing digital information. The most prevalent types of compact discs are those used

by the music industry to store digital recordings and CD-ROMs used to store computer

data. Both of these types of compact disc are read-only,

7. CD-R: - A compact disc recordable (CD-R) is a writable disc upon which a user can

write once and read many times. Once finalized, a CD-R disc cannot be formatted and

data cannot be deleted from it. A compact disc recordable is also known as a compact

disc - write once (CD-WO) or write once read many (WORM).

8. CD-WR: - CD–Read Writable (CD-RW) refers to an optical

CD that may be written and rewritten multiple times. CDRW

allows for data erasing during each rewritable session.

However, data cannot be changed during CD-RW sessions.

Some CD-RW discs have a multisession feature, in which

additional data may be written at a later time if extra space is

available.

9. DVD: - A digital versatile disc (DVD) is an optical disc storage medium similar to a

compact disc, but with enhanced data storage capacities as well as with higher quality

of video and audio format. Co-Developed by Sony, Panasonic, Philips and Toshiba in

1995, the DVD is widely used for video formats, audio formats as well software and

computer files. Digital versatile discs are also known as digital video discs.

10. DVD-RW: -Digital versatile disk rewritable (DVD-RW) is a write-once (read only)

digital versatile disc used to permanently store data files. It is an optical disc that

generally has a storage capacity of 4.71 gigabytes (GB/s), seven times larger than a

compact disc rewritable (CD-R) that holds around 700 megabytes (MB/s). When both

sides of a DVD-R are writable, it can store up to 17 GB/s of data.

11. Video Compact Disc (VCD): -A video compact disc (VCD) is a digital video format

used for storing video on standard compact discs. Video compact discs can be played

on dedicated video compact disc players, personal computers and other players such

as DVD players.


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12. Blu-Ray Disk (BD):- A Blu-ray disk (BD) is a high-capacity optical disk medium

developed for recording, rewriting and playing back high definition video. It can store

large amounts of data and was designed to supersede the DVD. Blu-ray was jointly

developed by a group of personal computer and consumer electronics companies called

the Blu-ray Disc Association. Blu-ray disks support higher resolutions and more

advanced video and audio formats compared to DVDs.

13. USB Flash Drive: - A USB flash drive is a device used for data storage that includes a

flash memory and an integrated Universal Serial Bus (USB) interface. Most USB

flash drives are removable and rewritable.

Physically, they are small, durable and reliable. The larger their storage space, the

faster they tend to operate. USB flash drives are mechanically very robust because

there are no moving parts. They derive the power to operate from the device to which

they are connected (typically a computer) via the USB port.

14. Memory Card: - A memory card is a type of storage device that is used for storing

media and data files. It provides a permanent and non-volatile medium to store data

and files from the attached device. Memory cards are commonly used in small, portable

devices, such as cameras and phones. A memory card is also known as a flash card.

15. Solid State Drive (SSD):- A solid state drive (SSD) is an electronic storage drive built

on solid state architecture. SSDs are built with NAND and NOR flash memory to store

non-volatile data and dynamic random access memory (DRAM). A SSD and magnetic

hard disk drive (HDD) share a similar purpose. A SSD is also known as a solid state

disk (SSD) or electronic disk drive.

UNIT-II

INPUT DEVICE:

Input devices provide input to a computer, while output devices provide a way for

a computer to output data for communication with users or other computers. An

I/O device is a device with both functionalities.

Some of the important input devices which are used in a computer –


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I. Keyboard

Keyboard is the most common and very popular input device which helps to input data

to the computer. The layout of the keyboard is like that of traditional typewriter,

although there are some additional keys provided for performing additional functions.

Keyboards are of two sizes 84 keys or 101/102 keys, but now keyboards with 104 keys

or 108 keys are also available for Windows and Internet. II. Mouse

Mouse is the most popular pointing device. It is a very famous cursor-control device

having a small palm size box with a round ball at its base, which senses the movement of

the mouse and sends corresponding signals to the CPU when the mouse buttons are

pressed.

Generally, it has two buttons called the left and the right button and a wheel is present

between the buttons. A mouse can be used to control the position of the cursor on the

screen, but it cannot be used to enter text into the computer.

Advantages

• Easy to use

• Not very expensive

• Moves the cursor faster than the arrow keys of the keyboard.

III. Joystick

Joystick is also a pointing device, which is used to move the cursor position on a

monitor screen. It is a stick having a spherical ball at its both lower and upper ends. The

lower spherical ball moves in a socket. The joystick can be moved in all four directions.

The function of the joystick is similar to that of a mouse. It is mainly used in Computer

Aided Designing (CAD) and playing computer games.

IV. Light Pen

Light pen is a pointing device similar to a pen. It is used to select a displayed menu item

or draw pictures on the monitor screen. It consists of a photocell and an optical system

placed in a small tube.

When the tip of a light pen is moved over the monitor screen and the pen button is pressed,

its photocell sensing element detects the screen location and sends the corresponding

signal to the CPU.


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V. Track Ball

Track ball is an input device that is mostly used in notebook or laptop computer, instead

of a mouse. This is a ball which is half inserted and by moving fingers on the ball, the

pointer can be moved.

Since the whole device is not moved, a track ball requires less space than a mouse. A track

ball comes in various shapes like a ball, a button, or a square.

VI. Scanner:

Scanner is an input device, which works more like a photocopy machine. It is used when

some information is available on paper and it is to be transferred to the hard disk of the

computer for further manipulation. Scanner captures images from the source which are

then converted into a digital form that can be stored on the disk. These images can be

edited before they are printed.

VII. Digitizer

Digitizer is an input device which converts analog information into digital form. Digitizer

can convert a signal from the television or camera into a series of numbers that

could be stored in a computer. They can be used by the computer to create a picture of

whatever the camera had been pointed at. Digitizer is also known as Tablet or Graphics

Tablet as it converts graphics and pictorial data into binary inputs. A graphic tablet as

digitizer is used for fine works of drawing and image manipulation applications.

VIII. Microphone

Microphone is an input device to input sound that is then stored in

a digital form. The microphone is used for various applications

such as adding sound to a multimedia presentation or for mixing

music.

IX. Magnetic Ink Card Reader (MICR)

MICR input device is generally used in banks as there are large number

of cheques to be processed every day. The bank's code


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number and cheque number are printed on the cheques with a special type of ink that

contains particles of magnetic material that are machine readable. This reading process is

called Magnetic Ink

Character Recognition (MICR). The main advantages of

MICR are that it is fast and less error prone.

X. Optical Character Reader (OCR)

OCR is an input device used to read a printed text. OCR scans the text optically, character

by character, converts them into a machine readable code, and stores the text on the system

memory.

XI. Bar Code Readers

Bar Code Reader is a device used for reading bar coded data (data in the form of light and

dark lines). Bar coded data is generally used in labeling goods, numbering the books, etc.

It may be a handheld scanner or may be

embedded in a stationary scanner. Bar Code Reader scans a bar code image, converts it

into an alphanumeric value, which is then fed to the computer that the bar code reader is

connected to.

XII. Optical Mark Reader (OMR)

OMR is a special type of optical scanner used to recognize the type of mark made by pen

or pencil. It is used where one out of a few alternatives is to be selected and marked. It is

specially used for checking the answer sheets of examinations having multiple choice

questions.

XIII. Digital Camera

A digital camera uses an electronic image sensor to create still photographs and record

video. The optical system of a digital camera works like a film camera, in which a typical

lens and diaphragm are used to adjust electronic image sensor lighting.

Digital cameras equip amateur and professional photographers with multiple automated

control functions. Advanced digital cameras facilitate manual control of most functions.

A digital camera is also known as a digicam.


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XIV. Voice Recognition

Voice recognition is a technique in computing technology by which specialized software

and systems are created to identify, distinguish and authenticate the voice of an individual

speaker.

Voice recognition evaluates the voice biometrics of an individual, such as the frequency

and flow of their voice and their natural accent. Voice recognition is also known as speaker

recognition.

XV. Touch Screen

A touch screen is a computer display screen that serves as an input device. When a touch

screen is touched by a finger or stylus, it registers the event and sends it to a controller for

processing. A touch screen may contain pictures or words that the user can touch to interact

with the device.

OUTPUT DEVICE:

An output device is any device used to send data from a computer to another device or

user. Most computer data output that is meant for humans is in the form of audio or video.

Thus, most output devices used by humans are in these categories. Examples include

monitors, projectors, speakers, headphones and printers.

1. Monitor:

A monitor is an electronic visual computer display that includes a screen, circuitry and the

case in which that circuitry is enclosed. Older computer monitors made use of cathode ray

tubes (CRT), which made them large, heavy and inefficient. Nowadays, flat-screen LCD

monitors are used in devices like laptops, PDAs and desktop computers because they are

lighter and more energy efficient. A monitor is also known as a screen or a visual display

unit (VDU).

Characteristics of Monitor:-

Following are the characteristics of a monitor:

a) Size: The most important aspect of a monitor is its size. Screen sizes are measured in

diagonal inches, the distance from one corner to another opposite corner diagonally.


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b) Resolution: The resolution of a monitor indicates how density the pixels are packed.

Pixel is short for picture element. A pixel is a single point in a graphic image.

Graphic monitors display pictures by dividing the display screen into millions of

pixels arranged in rows and columns. On color monitor each pixel is actually

composed of three dots namely a red, a green, and a blue. The quality of a display

monitor largely depends on its resolution.

c) Band Width: The amount of data that can be transmitted in a fixed amount of time.

For digital devices, the band width is usually expressed in bits or bytes per second (bps).

For analog devices it is expressed in cycle per second or Hertz (Hz).

d) Refresh Rate: Display monitors must be refresh many times per second. The refresh

rate determines how many times per seconds the screen is to be red drawn. The

refresh rate of a monitor is measured in Hertz. The faster the refreshers, the less the

monitor flickers.

e) Interlacing: It is a technique in which instead of scanning the image one line at a

time, it scans alternately i.e. alternate lines are scanned at each pass. It is used to keep

band width down. Since inter leaked displaced have been reported to be more flicker,

with better technology available, most monitors are non-interlaced now.

f) Dot per Inch: It is measured for the actual sharpness of the on screen image. This

depends on both the resolution & the size of the image. Practical experience shows

that a smaller screen has a sharper image at the same resolution than does a large

screen. This is because it will require more dots per inch to display the same number

of pixels.

g) Dot Pitch: A measurement that indicates the vertical distance between each pixel on a

display screen. It is measured in millimeter. The dot pitch is one of the principle

characteristics that determine the quality of display monitors.

h) Convergence: It refers to how sharply an individual color pixel on a monitor appears.

Each pixel is composed of three dots namely a red, a green and a blue. If the dots are

badly miss converged, the pixel will appear blurry.

Types of Computer Monitors

A computer monitor, technically termed as a visual display unit, can be plainly described

as an electronic device that transmits information from the computer onto a screen,

thereby acting as an interface and connecting the viewer with the computer. At present,

computer monitors are available in a variety of shapes, designs, and colors. However,


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based on the technology used to make computer monitors, they can be broadly

categorized into three types.

1. CRT (Cathode Ray Tube)

2. LCD (Liquid Crystal Display)

3. LED (Light-Emitting Diodes)

A. CRT (Cathode Ray Tube) Monitors

These monitors employ the CRT technology used most commonly in

the manufacturing of television screens. In this, a stream of intense

high energy electrons is used to form images on a fluorescent screen.

A cathode ray tube is a basically a vacuum tube containing an

electron gun at one end and a fluorescent screen at another end. From

this electron gun, a process called thermionic emission generates a

strong beam of electrons. These electrons travel through a narrow

path within the tube with high speed using various electro-magnetic

devices and finally strike the phosphor points present on the

fluorescent screen, thus creating an image.

B. LCD (Liquid Crystal Display) Monitors

Liquid crystal display, also known as liquid crystal diode, is one of the most advanced

technologies available at present. Typically, an LCD monitor consists of a layer of color

or monochrome pixels arranged schematically between a couple of transparent electrodes

and two polarizing filters. Optical effect is achieved by polarizing the light in varied

amounts and making it pass through the liquid crystal layer. At present, there are two types

of LCD technology available. These include the active matrix or TFT and a passive matrix

technology. Among these, TFT technology is more secure and reliable, and generates better

picture quality.

C. LED (Light-Emitting Diodes) Monitors

LED monitors are the latest types of monitors in the market today. Like LCD, it is again a

flat panel display making use of light-emitting diodes for back-lightning instead of Cold

Cathode Fluorescent (CCFL) back-lightning used in LCDs. Primarily, the display is of

LCD only but the back-lightning is done by LEDs.

LED monitors are said to use much lesser power than CRT and LCD. Thus, they are also

considered environmental friendly.


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Size of Monitor:-

Monitor size is measured by the distance from one corner of the screen's viewable area to

the diagonally opposite corner. With CRTs, the number is generally about an inch greater

than the actual area. Starting in the late 1990s, the real number is included in the specs.

For example, you might see a 17" monitor state 6.1" viewable. With flat panel monitors,

the screen size specification is actually its real size.

Digital monitor: -

A monitor that accepts digital rather than analog signals. All monitors (except flat-panel

displays) use CRT technology, which is essentially analog. The term digital, therefore,

refers only to the type of input received from the video adapter. A digital monitor then

translates the digital signals into analog signals that control the actual display.

Although digital monitors are fast and produce clear images, they cannot display

continuously variable colors. Consequently, only low-quality video standards, such as

MDA, CGA, and EGA, specify digital signals. VGA and SVGA, on the other hand, require

an analog monitor. Some monitors are capable of accepting either analog or digital signals.

Analog monitor:-

An analog monitor is a monitor capable of accepting continuously varying or analog

signals from the video adapter for an infinite range of different colors. The majority of all

CRT monitors are analog monitors and all flat-panel displays are digital.

Screen resolution:- The number of horizontal and vertical pixels on a display screen. The more pixels, the more

information is visible without scrolling. Screen resolutions have a pixel count such as

1600x1200, which means 1,600 horizontal pixels and 1,200 vertical pixels.

Refresh rate:-

The refresh rate is the number of times a display's image is repainted or refreshed per

second. The refresh rate is expressed in hertz so a refresh rate of 75 means the image is

refreshed 75 times in a second. The refresh rate for each display depends on the video card

used. You can change the refresh rate in the display properties.

Interlaced monitor: -An interlaced display is a cathode-ray tube (CRT) display in

which the lines are scanned alternately in two interwoven rasterized lines.In a CRT display,

there are several hundred horizontal lines in a frame (full screen). These lines are scanned

from left to right, and from top to bottom. The refresh rate (number of frames scanned per

second) varies, but it is normally between 60 and 100 hertz. Refresh rates slower than 60

Hz produce distracting screen flicker, which can cause headaches and eye fatigue.


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Non-interlaced Monitor: -A non-interlaced display is a cathode-ray tube (CRT)

display in which the lines are scanned sequentially from the top to the bottom of the screen.

In a CRT display, there are several hundred horizontal lines in a frame (full screen).

These lines are scanned from left to right, and from top to bottom. The refresh rate

(number of frames scanned per second) varies, but it is normally between 60 and 100 hertz.

Refresh rates slower than 60 Hz produce distracting screen flicker, which can cause

headaches and eye fatigue.

Dot Pitch Monitor: -Dot pitch is a term for the distance between individual pixels in a

visual display technology. It is calculated by measuring the closeness of individual pixels

to one another. A display with a lower dot pitch will generally have higher image quality.

Dot pitch is measured in fractions of a millimeter. Common dot pitch ranges for LCD

screens and monitors are around .20 - .28 millimeters. Experts point out that there are

different ways to measure dot pitch. Video standard

There are a variety of video standards that define the resolution and colors for displays.

Support for a graphics standard is determined both by the monitor and by the video adapter.

The monitor must be able to show the resolution and colors defined by the standard, and

the video adapter must be capable of transmitting the appropriate signals to the monitor.

Listed here, in approximate order of increasing power and sophistication, are the more

popular video standards for PCs. Note that many of these numbers represent only the

minimums specified in the standards. Many suppliers of video adapters provide greater

resolution and more colors.

• VGA -- 640 x 480 resolution

• SVGA -- 800 x 600 resolution

• XGA -- 1024 x 768 resolution

• SXGA -- 1280 x 1024 resolution

• UXGA -- 1600 x 1200 resolution

I. Video Graphics Array (VGA) Video Graphics Array (VGA) is a display standard

originally developed in 1987 by IBM for its PS2 range of computers. VGA’s single-

chip design facilitated direct computer system board embedding with minimum

requirements. Later, VGA became the de facto standard for graphics systems in PCs.

VGA was IBM's last graphical standard adopted by most manufacturers of clone

computers. Super Video Graphics Array (SVGA) and Extended Graphics Array (XGA)

replaced VGA.

II. Super Video Graphics Array (Super VGA or SVGA)


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Super video graphics array (Super VGA or SVGA) is a high-resolution standard used to

channel video data to a compatible visual output device - usually a computer monitor. This

is actually a broad umbrella term for other computer display standards. Originally, it was

just an extension to the VGA standard, which was a purely IBM-defined standard also

known as ultra-video graphics array (UVGA).

III. Extended Graphics Array (XGA)

Extended Graphics Array (XGA) is a computer display standard that provides 1,024 by

768 pixels in 256 colors, or 640 by 480 pixels in 16-bit color. It is a proprietary standard

that was originally intended to replace the earlier VGA (Video Graphics Array) display

mode, but as it was quickly replaced by superior technology, it instead became simply

known as part of the VGA family (with other formats like SVGA and UVGA).

2. Printer: A printer is an output device that prints paper documents. This includes text

documents, images, or a combination of both. The two most common types of

printers are inkjet and laser printers. The printed output produced by a printer is

often called a hard copy, which is the physical version of an electronic document.

While some printers can only print black and white hard copies, most printers today

can produce color prints. In fact, many home printers can now produce highquality

photo prints that rival professionally developed photos. This is because modern

printers have a high DPI (dots per inch) setting, which allows documents to print

with a very fine resolution.

Types of Printer a. Impact Printer:-An impact printer is a type of printer that works by direct

contact of an ink ribbon with paper. A metal or plastic head strikes the ink ribbon,

whereby the ribbon is pressed against the paper and the desired character (letter,

digit, dot, line) impression is printed on the sheet. Dot matrix, daisy-wheel and

ball printers are some commonly used types of impact printers.

b. Non-Impact Printer (NIP):- Printers are categorized according to whether or

not the image printed is formed by striking an ink ribbon against the paper.

Impact printers have physical contact; non-impact printers (NIPs) do not. Non-

impact printers are now most common, as they are faster and quieter than impact

printers.

c. Dot Matrix Printer (DMP):- A dot matrix printer (DMP) is a type of printer

which uses pins impacting an ink ribbon to print. These printers are generally


33

considered outdated, as they cannot create high-quality prints and are costly as

well. Therefore, they are mostly used in places where multipart forms are

required. A dot matrix printer is also known as an impact matrix printer.

d. Inkjet Printer: - Inkjet printers are a category of printer in which printing is done

with the help of inkjet

technology. The technology works by spraying ionized ink directed by

magnetic plates onto the paper, which is fed through the printer. As inkjet printers

are more affordable than other types of printers, they are commonly used as home

and business printers. Inkjet printers are also known simply as inkjets.

e. Laser Printer: -A laser printer is a type of printer that uses a laser and electrical

charge model instead of the traditional printing of ink onto paper. Laser printers

have increased the neatness and sophistication of print projects, with typical

resolutions of 600 dots per inch or higher.

f. Plotter: -A plotter is a computer vector graphic printer that gives a hard copy of

the output based on instructions from the system. Plotters are widely used to print

designs of things such as cars, ships and buildings on a piece of paper using a

pen. Plotters are different than a printer in that they are more precise and they are

most commonly used in engineering, where precision is mandatory. They are also

more expensive than ordinary printers. A plotter is also known as a graph plotter.

g. 3D Printing:-3D printing is a manufacturing process through which

threedimensional (3D) solid objects are created. It enables the creation of

physical 3D models of objects using a series of additive or layered development

framework, where layers are laid down in succession to create a complete 3D

object.3D printing is also known as additive manufacturing.

3. Sound Card

A sound card is an expansion component used in computers to receive and send audio.

Sound cards are configured and utilized with the help of a software application and a device

driver. The input device attached to receive audio data is usually a microphone, while the

device used to output audio data is generally speakers or headphones.

The sound card converts incoming digital audio data into


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analog audio so that the speakers can play it. In the reverse case, the sound card can convert

analog audio data from the microphone into digital data that can be stored on the computer

and altered using audio software. Sound cards are also known as audio adapters.

4. Speakers

Speakers are one of the most common output devices used with computer systems. Some

speakers are designed to work specifically with computers, while others can be hooked

up to any type of sound system. Regardless of their design, the purpose of speakers is to

produce audio output that can be heard by the listener.

Speakers are transducers that convert electromagnetic waves into sound waves. The

speakers receive audio input from a device such as a computer or an audio receiver. This

input may be either in analog or digital form. Analog speakers simply amplify the analog

electromagnetic waves into sound waves. Since sound waves are produced in analog form,

digital speakers must first convert the digital input to an analog signal, then generate the

sound waves.


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UNIT-3

Software: - Software, in its most general sense, is a set of instructions or programs

instructing a computer to do specific tasks. Software is a generic term used to describe

computer programs. Scripts, applications, programs and a set of instructions are all terms

often used to describe software.

The theory of software was first proposed by Alan Turing in 1935 in his essay "Computable

numbers with an application to the Entscheidungsproblem." However, the word software

was coined by mathematician and statistician John Tukey in a 1958 issue of American

Mathematical Monthly in which he discussed electronic calculators' programs.

Need of Software:-

Software is capable of performing many tasks, as opposed to hardware which can only

perform mechanical tasks that they are designed for. Software provides the means for

accomplishing many different tasks with the same basic hardware.

Types of Software:-

Software is often divided into three categories:

• System software: - It serves as a base for application software. System software

includes device drivers, operating systems (OSs), compilers, disk formatters, text

editors and utilities helping the computer to operate more efficiently. It is also

responsible for managing hardware components and providing basic non-

taskspecific functions. The system software is usually written in C programming

language.

• Programming software: - It is a set of tools to aid developers in writing programs.

The various tools available are compilers, linkers, debuggers, interpreters and text

editors.

• Application software: - It is intended to perform certain tasks. Examples of

application software include office suites, gaming applications, database systems

and educational software. Application software can be a single program or a

collection of small programs. This type of software is what consumers most typically

think of as "software."


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Operating System:-

An operating system (OS), in its most general sense, is software that allows a user to run

other applications on a computing device. While it is possible for a software application to

interface directly with hardware, the vast majority of applications are written for an OS,

which allows them to take advantage of common libraries and not worry about specific

hardware details.

The operating system manages a computer's hardware resources, including:

• Input devices such as a keyboard and mouse

• Output devices such as display monitors, printers and scanners

• Network devices such as modems, routers and network connections

• Storage devices such as internal and external drives

The OS also provides services to facilitate the efficient execution and management of, and

memory allocations for, any additional installed software application programs.

The OS consists of many components and features. The three most easily defined

components are:

• Kernel: This provides basic-level control over all of the computer hardware devices.

Main roles include reading data from memory and writing data to memory,

processing execution orders, determining how data is received and sent by devices

such as the monitor, keyboard and mouse, and determining how to interpret data

received from networks.

• User Interface: This component allows interaction with the user, which may occur

through graphical icons and a desktop or through a command line.

• Application Programming Interfaces: This component allows application developers

to write modular code.

Examples for OSs include Android, IOS, Mac OS X, Microsoft Windows and Linux.

Functions of operating system:-

Operating system performs the following functions: 1. Booting: Booting is a process of starting the computer operating system starts the

computer to work. It checks the computer and makes it ready to work.


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2. Memory Management: It is also an important function of operating system. The

memory cannot be managed without operating system. Different programs and data

execute in memory at one time. If there is no operating system, the programs may mix

with each other. The system will not work properly.

3. Loading and Execution: A program is loaded in the memory before it can be executed.

Operating system provides the facility to load programs in memory easily and then

execute it.

4. Data security: Data is an important part of computer system. The operating system

protects the data stored on the computer from illegal use, modification or deletion.

5. Disk Management: Operating system manages the disk space. It manages the stored

files and folders in a proper way.

6. Process Management: CPU can perform one task at one time. if there are many tasks,

operating system decides which task should get the CPU.

7. Device Controlling: Operating system also controls all devices attached to computer.

The hardware devices are controlled with the help of small software called device

drivers.

8. Printing controlling: Operating system also controls printing function. It a user issues

two print commands at a time, it does not mix data of these files and prints them

separately.

9. Providing interface: It is used in order that user interface acts with a computer

mutually. User interface controls how you input data and instruction and how

information is displayed on screen. The operating system offers two types of the

interface to the user:

• Graphical-line interface: It interacts with of visual environment to

communicate with the computer. It uses windows, icons, menus and other

graphical objects to issues commands.

• Command-line interface: it provides an interface to communicate with the

computer by typing commands.


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Device Driver

A device driver is a particular form of software application that is designed to enable

interaction with hardware devices. Without the required device driver, the

corresponding hardware device fails to work.

A device driver usually communicates with the hardware by means of the

communications subsystem or computer bus to which the hardware is connected.

Device drivers are operating system-specific and hardware-dependent. A device driver

acts as a translator between the hardware device and the programs or operating systems

that use it. A device driver may also be called a software driver.

Utility Software

Utility software helps to manage, maintain and control computer resources. Operating

systems typically contain the necessary tools for this, but separate utility programs can

provide improved functionality. Utility software is often somewhat technical and

targeted at users with a solid knowledge of computers. If you use a computer mostly

for e-mail, some Internet browsing and typing up a report, you may not have much need

for these utilities. However, if you are an avid computer user, these utilities can help

make sure your computer stays in tip-top shape.

Examples of utility programs are antivirus software, backup software and disk tools.

Microsoft Disk Operating System (MS-DOS)

The Microsoft Disk Operating System (MS-DOS) is an operating system developed for

PCs with x86 microprocessors. It is a command-line-based system, where all

commands are entered in text form and there is no graphical user interface.

MS-DOS was the most commonly used member of the family of disk operating systems.

It was the main choice as an operating system for IBM PC-compatible computer

systems during the 1980s to mid-1990s. MS-DOS was gradually replaced by systems

with graphical user interfaces, particularly Microsoft Windows.

MS-DOS was originally called 86-DOS. It was written by Tim Patterson (considered

the father of DOS) and owned by Seattle Computer Products. Microsoft bought 86DOS

for $75,000, licensed the software and released it with an IBM PC as MS-DOS

1.0 in 1982. MS-DOS was originally designed to run on any computer with an Intel

8086 processor, but the various hardware versions on these computers made

compatibility difficult. As a result, Microsoft provided hardware equipment


39

manufacturers with a development kit that could be used to tune the MS-DOS operating

system for the computer's specific hardware.

Features of DOS:

1. It is the primary system where the user will get an environment about the input

and output devices, e.g. Monitor, Keyboard, Printers etc.

2. It is helpful in performing file management e.g., creating, editing, deleting

files etc.

3. It is a single user operating system. One user can operate at one time in this

operating system.

4. It is a character Based interface system. We can type letters or characters in

this operating system.

WINDOW

A window is a graphical interface element used to display the contents of an application

for the user to view and interact with. A window is usually a rectangular area that can be

resized and is generally editable according to the capabilities and limitations imposed on

it by the application providing it. The window is essential in facilitating multitasking in a

modern operating system, as it allows users to visually and manually switch between

running applications and make general interactions with the operating system.

The concept of the window was first developed at the Stanford Research Institute by

Douglas Engelbert. Their earliest prototypes had multiple windows, but there was no way

of distinguishing between them because they had no borders, title bars or the other GUI

elements we know today. The research was continued at Xerox Palo Alto Research Center

(PARC) led by Alan Kay, which later in 1980s came up with the term WIMP, meaning

"window, icon, menu and pointer." Apple developed an interface based on WIMP and

used it in their Lisa computers. A little later Microsoft released its own OS with a

windowing system known simply as Microsoft Windows.

Qualities of a window:

• Occupies a certain area of the screen

• May or may not be visible at a given moment

• Responds to user and operating system events

• Generates itself

NCEC INSTITUTE OF SCIENCE & TECHNOLOGY , BHOPAL, 9893803508, 7771013508

40

Features of Windows Operating System

1. Speed

Even aside from incompatibilities and other issues that many people had with Vista, one of

the most straightforward was speed – it just felt too sluggish compared to XP, even on

pumped up hardware. Windows 7 brings a more responsive and sprightly feel and Microsoft

has spent a lot of time and effort getting the Start Menu response just right.

2. Compatibility

In simple terms, compatibility on Windows 7 will be far better than it was with Vista. Many

programs that individuals and companies used on Windows XP did not work immediately

and required updates, but with Windows 7 almost all applications that work on Vista should

still run.

3. Lower Hardware Requirements

Vista gained a reputation for making even the beefiest hardware look rather ordinary.

Windows 7, however, will run well on lower end hardware, making the transition from

Window XP less painful.

4. Search and Organization

One of the best things about Windows 7 is the improved search tool, which now rivals Mac

OS X’s Spotlight to be able to find what you need quickly and easily. For example, typing

‘mouse’ will bring up the mouse option within the control panel or typing a word will

display it and split it up neatly into files, folders and applications.

5. Safety and Security

New security features in Windows include two new authentication methods tailored towards

touchscreens (PINs and picture passwords), the addition of antivirus capabilities to

Windows Defender (bringing it in parity with Microsoft Security Essentials) Smart Screen

filtering integrated into Windows, and support for the "Secure 6. Interface and Desktop

Windows introduces significant changes to the operating system's user interface, many of

which are aimed at improving its experience on tablet computers and other touchscreen

devices. The new user interface is based on Microsoft's Metro design language, and uses a

Start screen similar to that of Windows Phone as the primary means of launching

applications.

7. Taskbar/Start menu


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At first glance, the task bar looks like nothing has much has changed since Vista. In fact,

that’s not the case and it’s a lot more powerful. Microsoft is now making best use of its aero

technology. By default, taskbar icons are now larger and items are grouped together and are

not labelled with clumsy text.

Programming Language: A programming language is a computer language

engineered to create a standard form of commands. These commands can be interpreted

into a code understood by a machine. Programs are created through programming languages

to control the behavior and output of a machine through accurate algorithms, similar to the

human communication process.

A programming language is also known as a programming system, computer language or

computer system. A programming language is typically divided into two elements: syntax

and semantics. There is pretty much always a specification document to define both

elements. For example, an ISO standard defines C, while Perl has a dominant

implementation used as a reference. An algorithm is described using the programming language. Programming languages are

typically called computer languages; however, some authors deem programming languages

to be subsets of computer languages. Since the oldest forms of programming languages like

COBOL and FORTRAN, thousands of computer languages have been developed.

Types of Programming Languages: There are two types of programming languages, which can

be categorized into the following ways:

1. Low level language

a) Machine language (1GL)

b) Assembly language (2GL)

2. High level language

a) Procedural-Oriented language (3GL)

b) Problem-Oriented language (4GL)

c) Natural language (5GL)

1. Low level language

This language is the most understandable language used by computer to perform its operations.

It can be further categorized into:

i. Machine Language (1GL)


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Machine language consists of strings of binary numbers (i.e. 0s and 1s) and it is the only

one language, the processor directly understands. Machine language has an Merits of very

fast execution speed and efficient use of primary memory.

Merits:

It is directly understood by the processor so has faster execution time since the

programs written in this language need not to be translated. It doesn’t need larger

memory.

Demerits:

It is very difficult to program using 1GL since all the instructions are to be represented by

0s and 1s.

Use of this language makes programming time consuming.

It is difficult to find error and to debug.

It can be used by experts only. ii. Assembly Language

Assembly language is also known as low-level language because to design a program

programmer requires detailed knowledge of hardware specification. This language uses

mnemonics code (symbolic operation code like ‘ADD’ for addition) in place of 0s and 1s.

The program is converted into machine code by assembler. The resulting program is

referred to as an object code.

Merits:

It is makes programming easier than 1GL since it uses mnemonics code for programming.

It makes programming process faster.

Error can be identified much easily compared to 1GL. It is easier to debug than

machine language.

Demerits:

Programs written in this language is not directly understandable by computer so translators.

It is hardware dependent language so programmers are forced to think in terms of

computer’s architecture rather than to the problem being solved.

Being machine dependent language, programs written in this language are very less or not

portable.

Programmers must know its mnemonics codes to perform any task.

2. High level language

An instruction of this language closely resembles to human language or English like words.

It uses mathematical notations to perform the task. The high level language is easier to

learn. It requires less time to write and is easier to maintain the errors. The high level


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language is converted into machine language by one of the two different languages

translator programs; interpreter or compiler.

High level language can be further categorized as:

i. Procedural-Oriented language (3GL)

Procedural Programming is a methodology for modeling the problem being solved, by

determining the steps and the order of those steps that must be followed in order to reach a

desired outcome or specific program state. These languages are designed to express the

logic and the procedure of a problem to be solved. It includes languages such as Pascal,

COBOL, C, FORTAN, etc.

Merits:

Because of their flexibility, procedural languages are able to solve a variety of problems.

Programmer does not need to think in term of computer architecture which makes them

focused on the problem.

Programs written in this language are portable.

Demerits:

It is easier but needs higher processor and larger memory.

It needs to be translated therefore its execution time is more.

ii. Problem-Oriented language (4GL)

It allows the users to specify what the output should be, without describing all the details of

how the data should be manipulated to produce the result. This is one step ahead from 3GL.

These are result oriented and include database query language. E.g.: Visual Basic, C#, PHP,

etc.

The objectives of 4GL are to:

Increase the speed of developing programs.

Minimize user’s effort to obtain information from computer.

Reduce errors while writing programs.

Merits:

Programmer need not to think about the procedure of the program. So, programming

is much easier.

Demerits:

It is easier but needs higher processor and larger memory.

It needs to be translated therefore its execution time is more.


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Assembler

An assembler is a type of computer program that interprets software programs written in

assembly language into machine language, code and instructions that can be executed by a

computer.

An assembler enables software and application developers to access, operate and manage a

computer's hardware architecture and components.

An assembler is sometimes referred to as the compiler of assembly language. It also provides the

services of an interpreter.

An assembler primarily serves as the bridge between symbolically coded instructions

written in assembly language and the computer processor, memory and other computational

components. An assembler works by assembling and converting the source code of

assembly language into object code or an object file that constitutes a stream of zeros and

ones of machine code, which are directly executable by the processor.

Compiler

A compiler is a software program that transforms high-level source code that is written by

a developer in a high-level programming language into a low level object code (binary code)

in machine language, which can be understood by the processor. The process of converting

high-level programming into machine language is known as compilation.

The processor executes object code, which indicates when binary high and low signals are

required in the arithmetic logic unit of the processor.

A compiler that converts machine language into high-level natural language is called a

decompiler. Compilers that produce the object code meant to run on a system are called

cross-compilers. Finally, a compiler that converts one programming language into another

is called a language translator.

A compiler executes four major steps:

• Scanning: The scanner reads one character at a time from the source code and keeps

track of which character is present in which line.

• Lexical Analysis: The compiler converts the sequence of characters that appear in

the source code into a series of strings of characters (known as tokens), which are

associated by a specific rule by a program called a lexical analyzer. A symbol table

is used by the lexical analyzer to store the words in the source code that correspond

to the token generated.


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• Syntactic Analysis: In this step, syntax analysis is performed, which involves

preprocessing to determine whether the tokens created during lexical analysis are in

proper order as per their usage. The correct order of a set of keywords, which can

yield a desired result, is called syntax. The compiler has to check the source code to

ensure syntactic accuracy.

• Semantic Analysis: This step is comprised of several intermediate steps. First, the

structure of tokens is checked, along with their order with respect to the grammar in

a given language. The meaning of the token structure is interpreted by the parser and

analyzer to finally generate an intermediate code.

Interpreter

An interpreter is a computer program that is used to directly execute program instructions

written using one of the many high-level programming languages. The interpreter

transforms the high-level program into an intermediate language that it then executes, or it

could parse the high-level source code and then performs the commands directly, which is

done line by line or statement by statement.

An interpreter transforms or interprets a high-level programming code into code that can be

understood by the machine (machine code) or into an intermediate language that can be

easily executed as well. The interpreter reads each statement of code and then converts or

executes it directly. In contrast, an assembler or a compiler converts a high-level source

code into native (compiled) code that can be executed directly by the operating system.

Application Software

Application software is a program or group of programs designed for end users. These

programs are divided into two classes: system software and application software. While

system software consists of low-level programs that interact with computers at a basic level,

application software resides above system software and includes applications such as

database programs, word processors and spreadsheets. Application software may be

bundled with system software or published alone. Application software may simply be

referred to as an application.

Types of Software Applications


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The following table describes different kinds of software applications that would be suitable for different tasks:

1. Word Processing software - Use this kind of tool to create worksheets, type letters, and type

papers, etc.

Ex- MS Word, WordPerfect, MS Works, AppleWorks

2. Desktop Publishing software - Use this software to make signs, banners, greeting cards,

illustrative worksheets, newsletters, etc.

Ex-Adobe PageMaker, MS Word, MS Publisher, AppleWorks, MS Works, Quark Express

3. Spreadsheet software - Use this kind of tool to compute number-intensive problems such as

budgeting, forecasting, etc. A spreadsheet will plot nice graphs very easily.

Ex-MS Excel, Quattro Pro, Lotus 1-2-3, MS Works, AppleWorks.

4. Database software - Use this software to store data such as address, membership and other

text information. A database can be used to easily sort and organize records.

Ex-MS Access, Filemaker Pro, AppleWorks, MS Works

5. Presentation software - Use this software to create multimedia stacks of cards/screens that

can effectively present a lesson or a sales pitch. The user often clicks on buttons to advance

to the next screen in a sequence.

Ex-MS PowerPoint, AppleWorks (slideshows), HyperStudio, Flash, Director, HyperCard,

Digital Chisel, SuperCard, Corel Envoy.

6. Internet Browsers - This software allows one to surf the Web. Often they can read email and

create Web pages too.

Ex-Netscape Navigator (or Netscape Communicator), MS Internet Explorer, AOL Browser.

7. Email programs - These programs send and receive email.

Ex-Netscape Messenger (part of Netscape Communicator), MS Outlook Express, MS Outlook,

Eudora, AOL browser (has email built in).


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8. Graphics Programs (pixel-based) - This software allows one to touch up photographs and

create graphics from scratch.

Ex-Adobe Photoshop, Paint Shop Pro, AppleWorks, MS Works, MS Paint (comes free on

Windows PC's), Painter.

9. Graphics Programs (vector-based) - This software creates graphics that are similar to

illustrations or cartoon drawings.

Ex-Adobe Illustrator, Corel Draw, AppleWorks, MS Works, MS Word.

10. Communications software - This software allows two computers with modems to

communicate through audio, video, and/or chat-based means.

Ex-MS NetMeeting, AOL Instant Messenger, IRC, ICQ, CU-SeeMe.

Computer Coding System:

A coding system used for transmitting messages requiring brevity or secrecy. Code,

computer code. (Computer science) the symbolic arrangement of data or instructions in a

computer program or the set of such instructions. Access, access code.

1. American Standard for Information Interchange (ASCII)

American Standard for Information Interchange (ASCII) is a method of encoding characters that

is based on the order of alphabetic characters in the English language.

ASCII integer representations have printable and nonprintable subsets. Printable characters

are normal characters, and nonprintable characters are characters used to represent keyboard

keys, e.g., backspace, delete, and return.

Technically, ASCII is 7-bit representing only 128 characters (0-127). The range 0-31 are control

characters, with 32-127 representing alphabetical characters from A to Z, numerals from 0 to 9

and punctuation marks (though not in that order). ASCII only may be used to encode U.S.

English.

Some people confuse codes above 128-255 to be ASCII, but technically speaking, they are

not. As computers evolved, it became common to use an 8-bit byte. This last character

allowed for an extra 128 characters, which is known as extended ASCII. Different systems

implement extended ASCII differently, so there are compatibility issues that aren't

encountered in the first 128 characters.


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2. Indian Script Code for Information Interchange (ISCII)

ISCII is a coding scheme for representing various writing systems of India. It encodes the

main Indic scripts and a Roman transliteration. The supported scripts are: Assamese,

Bengali, Bangla, Devanagari, Gujarati, Gurumukhi, Kannada, Malayalam, Oriya, Tamil,

and Telugu. ISCII does not encode the writing systems of India based on Arabic, but its

writing system switching codes nonetheless providefor Kashmiri, Sindhi, Urdu, Persian,

Pashto and Arabic. The Arabic-based writing systems were subsequently encoded in the

PASCII encoding.

ISCII has not been widely used outside certain government institutions and has now been

rendered largely obsolete by Unicode. Unicode uses a separate block for each Indic writing

system, and largely preserves the ISCII layout within each block.

3. Unicode

Unicode is a modern standard for text representation that defines each of the letters and

symbols commonly used in today’s digital and print media. Unicode has become the top

standard for identifying characters in text in nearly any language.

Developed in the 1980s, Unicode represented a step toward a more global strategy for text

representation than the previously used American Standard Code for Information

Interchange (ASCII). Different versions of Unicode have allowed for the representation of

diverse languages, including Hebrew and Arabic, which are read differently than texts that

use Western alphabets, and languages like Chinese, where more complex glyphs are used

in place of individual letters representing a single phonetic sound.

Unicode is allowing for easier standardization of print or digital media conventions,

whether for the printed page, or for devices such as smartphones. Unicode is maintained by

the Unicode Consortium, a nonprofit that exists to advance the Unicode standard in order

to make it easier to deal with cross-platform changes or other new representations of text

across new media and technologies.

Number System:

The technique to represent and work with numbers is called number system. Decimal

number system is the most common number system. Other popular number systems include

binary number system, octal number system, hexadecimal number system, etc.

Types of Number System


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Four main types of number system. The types are: 1. Decimal System 2. Binary System 3.

The Octal System 4. The Hexadecimal System.

1. Decimal System:

In decimal system the base (or radix) is 10, since any position can contain one of ten digits,

refer (3) above. The system therefore has a carrying factor of 10 and each digit indicates a

value which depends on the position it occupies, for example;

In 6421 the digit 6 signifies 6 x 1000

In 4621 the digit 6 signifies 6 x 100

The decimal system uses ten digits to record the number. The ten digits are 0, 1, 2, 3, 4, 5, 6,

7, 8 and 9 and any number (used) is based upon power of 10.

For example 5281 is made up of:

ADVERTISEMENTS:

(5 x 103) + (2 x 102) + (8 x 101) + (1 x 100) = 5000

+ 200 + 80 + 1 = 5281.

2. Binary System:

Whereas decimal system uses ten digits to record the number, the binary system uses only

two digits (for recording the number) that is 0 and 1, and its base is 2 (whereas that of

decimal system is 10). Although in everyday life, people generally use the decimal number

system for counting, it is more convenient to use the binary number system in a computer

because electronic components are usually in one of two states, which can be used to

represent 0 and 1, the two digits used in the binary system.

The computer does not have a large number of symbols for representing data. It has only

two, 0 and 1 (called binary digits or bits). These correspond to the two electronic or

magnetic states used in computer circuits and storage.

For example if a punched paper tape is used in the computer, a hole in a tape may allow

electrical contact to be made (ON) and the absence of a hole in the tape does not allow

electrical contact to be made (OFF). Therefore a hole can represent 1 and no hole can

represent 0. Binary system is more compact than the decimal system of coding as the latter

will need large size of the storage medium and relative complexity of the reading device.


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(a) Let the decimal number be 217.

To find the binary equivalent proceed as follows:

Given below is the table of construction of Binary numbers:

Conversion of a Decimal Number to Binary Equivalent:


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Start binary number with last digit. Therefore the binary equivalent of 217 is 11011001.

(b) Convert .8125 into binary number.

(c) Convert decimal number 217.8125 into binary number

From (a) and (b) above =

3. The Octal System:

The octal system (base 8) and hexadecimal system (base 16) are of importance because they

can be used as a shorthand for binary numbers. This is because three binary digits can be

represented by the numbers 0 to 7 i.e., the octal range, while four binary digits can be

represented by the numbers 0 to 9 and A to F.


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Let octal number be (235)8

Hence (235)8 = (157)10

(b) Conversion of decimal number into octal equivalent

Let the decimal number be 692.625

( a) Conversion of Octal number into Decimal equivalent


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(c) Convert (413.2)8 into Decimal equivalent

4. The Hexadecimal System:

The hexadecimal system has a base 16 and the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and letters A,

B, C, D, E, and F are used. The letters A, B, C, D, E and F represent the decimal numbers

10, 11, 12, 13, 14 and 15 respectively.

(a) Conversion of decimal number (259.8125)10 into hexadecimal form

(b) Conversion of hexadecimal number B2F.5 into Decimal equivalent.


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When hexadecimal is used to represent a binary number, the individual hexadecimal digits

represent successive groups of four binary digits starting at the point. This is similar to the

conversion from binary to octal, in which each set of three bits is translated to an octal digit.

UNIT-4

Use of Communication and IT

Information and communications technology or (ICT) is extensional term for information

technology (IT) that stresses the role of unified communications and the integration of

telecommunications (telephone lines and wireless signals), computers as well as necessary

enterprise software, middleware, storage, and audio-visual systems, which enable users to

access, store, transmit, and manipulate information.

The term ICT is also used to refer to the convergence of audio-visual and telephone

networks with computer networks through a single cabling or link system. There are large

economic incentives (huge cost savings due to elimination of the telephone network) to

merge the telephone network with the computer network system using a single unified

system of cabling, signal distribution and management.


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ICT is a broad subject and the concepts are evolving. The term covers any product that will

store, retrieve, manipulate, transmit or receive information electronically in a digital form,

e.g. personal computers, digital television, email, robots. For clarity, Zuppo provided an

ICT hierarchy where all levels of the hierarchy "contain some degree of commonality in

that they are related to technologies that facilitate the transfer of information and various

types of electronically mediated communications". Skills Framework for the Information

Age is one of many models for describing and managing competencies for ICT

professionals for the 21st century.

Communication Process

The Communication is a two-way process wherein the message in the form of ideas,

thoughts, feelings, opinions is transmitted between two or more persons with the intent of

creating a shared understanding.

Simply, an act of conveying intended information and understanding from one person to

another is called as communication. The term communication is derived from the Latin

word “Communis” which means to share. Effective communication is when the message

conveyed by the sender is understood by the receiver in exactly the same way as it was

intended.

Communication Process $ component of communication

The communication is a dynamic process that begins with the conceptualizing of ideas by the

sender who then transmits the message through a channel to the receiver, who in turn gives the

feedback in the form of some message or signal within the given time frame. Thus, there are

seven major elements of communication process:

https://businessjargons.com/wp-content/uploads/2016/03/communication-process.jpg


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Sender: The sender or the communicator is the person who initiates the conversation and has

conceptualized the idea that he intends to convey it to others.

Encoding: The sender begins with the encoding process wherein he uses certain words or

non-verbal methods such as symbols, signs, body gestures, etc. to translate the information

into a message. The sender’s knowledge, skills, perception, background, competencies, etc.

has a great impact on the success of the message.

Message: Once the encoding is finished, the sender gets the message that he intends to

convey. The message can be written, oral, symbolic or non-verbal such as body gestures,

silence, sighs, sounds, etc. or any other signal that triggers the response of a receiver.

Communication Channel: The Sender chooses the medium through which he wants to

convey his message to the recipient. It must be selected carefully in order to make the

message effective and correctly interpreted by the recipient. The choice of medium depends

on the interpersonal relationships between the sender and the receiver and also on the

urgency of the message being sent. Oral, virtual, written, sound, gesture, etc. are some of

the commonly used communication mediums.

Receiver: The receiver is the person for whom the message is intended or targeted. He tries

to comprehend it in the best possible manner such that the communication objective is

attained. The degree to which the receiver decodes the message depends on his knowledge

of the subject matter, experience, trust and relationship with the sender.

Decoding: Here, the receiver interprets the sender’s message and tries to understand it in

the best possible manner. An effective communication occurs only if the receiver

understands the message in exactly the same way as it was intended by the sender.

Feedback: The Feedback is the final step of the process that ensures the receiver has

received the message and interpreted it correctly as it was intended by the sender. It

increases the effectiveness of the communication as it permits the sender to know the

efficacy of his message. The response of the receiver can be verbal or non-verbal.

Transmission Modes in Computer Networks

Transmission mode means transferring of data between two devices. It is also known as

communication mode. Buses and networks are designed to allow communication to occur

between individual devices that are interconnected. There are three types of transmission

mode:-


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Simplex Mode

Half-Duplex Mode

Full-Duplex Mode

Simplex Mode

In Simplex mode, the communication is unidirectional, as on a one-way street. Only one of

the two devices on a link can transmit, the other can only receive. The simplex mode can

use the entire capacity of the channel to send data in one direction. Example: Keyboard and

traditional monitors. The keyboard can only introduce input, the monitor can only give the

output.

Half-Duplex Mode:

In half-duplex mode, each station can both transmit and receive, but not at the same time.

When one device is sending, the other can only receive, and vice versa. The half-duplex

mode is used in cases where there is no need for communication in both direction at the

same time. The entire capacity of the channel can be utilized for each direction. Example:

Walkie- talkie in which message is sent one at a time and messages are sent in both the

directions.


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Full-Duplex Mode:

In full-duplex mode, both stations can transmit and receive simultaneously. In full duplex

mode, signals going in one direction share the capacity of the link with signals going in

other direction, this sharing can occur in two ways:

Either the link must contain two physically separate transmission paths, one for sending and

other for receiving.

Or the capacity is divided between signals travelling in both directions.

Full-duplex mode is used when communication in both direction is required all the time.

The capacity of the channel, however must be divided between the two directions. Example:

Telephone Network in which there is communication between two persons by a telephone

line, through which both can talk and listen at the same time.

Communication channel


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A communication channel or simply channel refers either to a physical transmission

medium such as a wire, or to a logical connection over a multiplexed medium such as a

radio channel in telecommunications and computer networking.

Twisted pair wire.

Coaxial cable.

Fiber optic cable.

Twisted Pair Cable: Twisted pair cable is one of the most commonly used communication

media. It is used in local area network (LAN) for data communication between different

computers. It is also used in telephone lines to carry voice and data signals.

A twisted pair cable consists of a pair of thin diameter copper wires. These wires are covered

by insulating material (such as plastic). These pair of wires are twisted together to form a

cable. The wires are twisted around each other to minimize (or reduce) interference from

other twisted pairs in the cable.

The data transmission speed through twisted pair cable is about 9600 bits per second in a

distance of 100 meters. However, this transmission speed is less than coaxial cable or

optical fiber.

The twisted pair cable has been the standard communication channel for voice and data

communication. But now its use is reducing because today more reliable communication

media are available such as coaxial cable, fiber optic cable microwave and satellite.

Coaxial Cable: Coaxial cable is also referred to as Coax. It carries signals of higher

frequency ranges than twisted-pair cable. Coaxial cable consists of a single solid copper

wire, which is called the inner conductor.

Coaxial cable can be used for telephone lines for voice and data transmission with very high

frequency. The bandwidth of coaxial cable is 80 times greater than that of twisted pair

media. Coaxial cable is also widely used in local area network (LAN). It is more expensive

than twisted-pair wire.

Fiber-Optic Cable: In twisted-pair cable and coaxial cable, data is transmitted in the form

of electric frequencies. The fiber optic cable uses light to transmit data. The data

transmission speed is very high (because fiber-optic cable uses light to transmit data). The

data transmission speed is up to billions bits per second. Today, most of the telephone

companies and cable TV operators are using fiber optic cables in their networks.

Modem

A modem is a network device that both modulates and demodulates analog carrier signals

(called sine waves) for encoding and decoding digital information for processing. Modems


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accomplish both of these tasks simultaneously and, for this reason, the term modem is a

combination of "modulate" and "demodulate."

Client/server

What's the difference between client/server and peer-to-peer networks? In terms of security

and cost, quite a lot. Brien Posey discusses these differences and offers advice on picking a

networking architecture that's right for you.

If you work with computers long enough, sooner or later you’ll hear the terms

“client/server” and “peer-to-peer.” These terms may seem strange at first, but each describes

a particular networking architecture. And each architecture is more suitable for certain types

of businesses.

Peer-to-peer networks should be installed in homes or in very small businesses where

employees interact regularly. They are inexpensive to set up (comparatively speaking);

however, they offer almost no security. On the other hand, client/server networks can

become as big as you need them to be. Some support millions of users and offer elaborate

security measures. As you can imagine, client/server networks can become very expensive.

Peer-to-peer networks

Peer-to-peer networks are appropriate only for very small businesses or for home use. A

peer-to-peer network can support about ten clients (workstations) before it begins to suffer

from some serious performance and management problems. Usually, peer-to-peer networks

are composed of a collection of clients that run either Windows NT Workstation or

Windows 98. Windows 3.11, Windows 95, and Windows 2000

Professional also support peer-to-peer networking.

The concept behind peer-to-peer networking is to share files and printers as inexpensively

as possible; therefore, there’s no main server on the network. Instead, each client functions

both as a client and as a server simultaneously. Since users are allowed to control access to

the resources on their own computers, however, security becomes very risky in a peer-to-

peer environment. There’s no central security or any way to control who shares what. Users

are free to create any network share points on their computers. The only security on a peer-

to-peer network is at the share level. When users create network shares, they may implement

no security, which means that anyone can have full access to the share, or they may assign

a password to the share. Depending on which networking platform you use, a user may be

able to assign one password to a share for read-only access and another password for full

control over the share.


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Although this arrangement may sound somewhat secure, it isn’t. The computer that contains

the shared resources doesn’t check on who’s trying to access those resources. Any user can

access them as long as the user knows the password. If someone happens to write down a

password, anyone who finds that password can access the share.

Client/server networks

There are an almost infinite variety of client/server networks, but all of them have a couple

of things in common. For one thing, all have centralized security databases that control

access to shared resources on servers. In the world of Windows, the server usually runs

NetWare, Windows NT, or one of the Windows 2000 Server products. The server contains

a list of usernames and passwords. Users can’t log on to the network unless they supply

valid usernames and passwords to the server. Once logged on, users may access only those

resources that the network administrator allows them to access. Thus, client/server networks

possess much more security than do peer-to-peer networks.

Client/server networks also tend to be much more stable. In a peer-to-peer network, certain shared

resources reside on each user’s machine. If users decide to monkey around and crash their

computers, they could seriously affect their peer-to-peer network (where coworkers depend on

resources that reside on other users’ machines). On most client/server networks, however, shared

resources reside on the server, where they’re safe from curious users. If a user happens to erase a

shared resource from the server, you can rely on the nightly backup. (It’s very difficult to back

up a peer-to-peer network every night.)

The primary downside to a client/server network is its cost. Servers can become very

expensive. For example, you could pay over $800 for a copy of Windows NT Server and

five client licenses, and that price doesn’t even include the cost of the hardware, which must

be more powerful than a standard workstation. Additionally, client/server networks require

an employee to manage them. Unless you have someone in your office who’s trained in

NetWare or Windows NT Server and in all of the issues that are involved in client/server

networking, you’ll have to hire someone from the outside. And believe me when I say that

qualified networking professionals don’t come cheap.

Types of Connections and Advantages and Disadvantages

Dial-Up Connection- Dial-up connections are a connection between two devices using

standard telephone service. When this connection is initiated, it is done so by a device that


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picks up a regular telephone line. It picks up the line and listens for a dial tone. Once it hears

a dial tone, it dials a standard telephone number of the receiving device, which is also

connected to a regular telephone line. So, it is called dial-up because the devices literally

dial each other up to connect.

Uses of a Dial Up Connection

Dial-up connections are found almost any place that telephone lines and computers coexist.

It is also used by credit card processing equipment, electronic bulletin boards, email

machines, serial networks and more.

Speed of dial up connections

The condition of the telephone line has a lot to do with the maximum speed of the dial up

connection. Under optimal circumstances, a 56kbps throughput can be maintained. Real

world speeds typically vary between 18kbps and 48kbps.

Leased lines -Leased lines are most commonly rented by businesses to connect branch

offices of the organization. Leased lines guarantee bandwidth for network traffic between

locations. For example, T1 leased lines are common and offer the same data rate as

symmetric DSL.

Individuals can theoretically rent leased lines for high-speed internet access, but their high

cost deters most people, and far more affordable home options are available with higher

bandwidth than a simple dial-up phone line, including residential DSL and cable internet

broadband service.

Fractional T1 lines, starting at 128 Kbps, reduce this cost somewhat. They can be found in

some apartment buildings and hotels.

ISDN- An ISDN line is a digital line - your computer connects to the ISDN line (via a

terminal adaptor) without having to convert the data into sound first. A basic rate ISDN

lineprovides two 'channels', each of which can be used for separate calls, thus equivalentto

having two regular lines.

DSL-DSL, which stands for Digital Subscriber Line, uses existing 2-wire copper telephone

line connected to one's home so service is delivered at the same time as landline telephone

service. Customers can still place calls while surfing the Internet.

RF- A coaxial RF connector (radio frequency connector) is an electrical

connectordesigned to work at radio frequencies in the multi-megahertz range. RF connectors

are typically used with coaxial cables and are designed to maintain the shielding that the

coaxial design offers.


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Broad band uses-In telecommunications, broadband is wide bandwidth data transmission which

transports multiple signals and traffic types.

In the context of Internet access, broadband is used to mean any high-speed Internet access

that is always on and faster than dial-up access over traditional analog or ISDN PSTN

services.

Types of network

Local Area Network (LAN)

We’re confident that you’ve heard of these types of networks before – LANs are the most

frequently discussed networks, one of the most common, one of the most original and one

of the simplest types of networks.

LANs connect groups of computers and low-voltage devices together across short distances

(within a building or between a group of two or three buildings in close proximity to each

other) to share information and resources. Enterprises typically manage and maintain LANs.

Using routers, LANs can connect to wide area networks (WANs, explained below) to rapidly and

safely transfer data.

Metropolitan Area Network (MAN)

These types of networks are larger than LANs but smaller than WANs – and incorporate elements

from both types of networks.

MANs span an entire geographic area (typically a town or city, but sometimes a campus).

Ownership and maintenance is handled by either a single person or company (a local

council, a large company, etc.).

Wide Area Network (WAN)

Slightly more complex than a LAN, a WAN connects computers together across longer physical

distances.

This allows computers and low-voltage devices to be remotely connected to each other over one

large network to communicate even when they’re miles apart.

The Internet is the most basic example of a WAN, connecting all computers together around

the world. Because of a WAN’s vast reach, it is typically owned and maintained by multiple

administrators or the public.

Virtual Private Network (VPN)


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By extending a private network across the Internet, a VPN lets its users send and receive

data as if their devices were connected to the private network – even if they’re not. Through

a virtual point-to-point connection, users can access a private network remotely.

1. Mesh Topology

In a mesh network, devices are connected with many redundant interconnections between

network nodes. In a true mesh topology every node has a connection to every other node in

the network. There are two types of mesh topologies

Full mesh topology: occurs when every node has a circuit connecting it to every other node

in a network. Full mesh is very expensive to implement but yields the greatest amount of

redundancy, so in the event that one of those nodes fails, network traffic can be directed to

any of the other nodes. Full mesh is usually reserved for backbone networks.

Partial mesh topology: is less expensive to implement and yields less redundancy than full

mesh topology. With partial mesh, some nodes are organized in a full mesh scheme but

others are only connected to one or two in the network. Partial mesh topology is commonly

found in peripheral networks connected to a full meshed backbone.

2. Star Topology

In a star network devices are connected to a central computer, called a hub. Nodes communicate

across the network by passing data through the hub.

Main Advantage: In a star network, one malfunctioning node doesn't affect the rest of the

network.

Main Disadvantage: If the central computer fails, the entire network becomes unusable.


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3. Bus Topology

In networking a bus is the central cable -- the main wire -- that connects all devices on a

local-area network (LAN). It is also called the backbone. This is often used to describe the

main network connections composing the Internet. Bus networks are relatively inexpensive

and easy to install for small networks. Ethernet systems use a bus topology.

Main Advantage: It's easy to connect a computer or device and typically it requires less cable

than a star topology.

Main Disadvantage: The entire network shuts down if there is a break in the main wire and it

can be difficult to identify the problem if the network shuts down.

4. Ring Topology

A local-area network (LAN) whose topology is a ring. That is, all of the nodes are connected

in a closed loop. Messages travel around the ring, with each node reading those messages

addressed to it.

Main Advantage: One main advantage to a ring network is that it can span larger distances

than other types of networks, such as bus networks, because each node regenerates

messages as they pass through it.

5. Tree Topology

This is a "hybrid" topology that combines characteristics of linear bus and star topologies.

In a tree network, groups of star-configured networks are connected to a linear bus

backbone cable.


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Main Advantage: A Tree topology is a good choice for large computer networks as the

tree topology "divides" the whole network into parts that are more easily manageable. Main

Disadvantage: The entire network depends on a central hub and a failure of the central hub

can cripple the whole network.

Component of LAN

Network Interface Cards (NIC)

Each networked device contains a Network Interface Card. The NIC may be a separate

board installed into a computer’s slot, or it may be built into the motherboard. Either way,

the NIC is the bridge between the computer and the network, and is a gatekeeper of sorts,

because it decides whether to process a data packet or not, either passing it on to the

computers processor or discarding it based on the destination address in the packet. The

NIC also takes information from the processor, formats it for transmission and puts it on

the wire.

Hubs

A hub is the central wiring connector on a LAN, where all of the network cables come

together. Each cable plugs into a port on the hub. The hub accepts incoming data packets

from devices on the network and transmits them to all other computers attached to the hub.

Each device NIC receives each packet and makes its process or discard decision.

Switches

A switch is like a hub in that it is a central point for connecting network cables; however, a

switch is able to receive a packet and transmit it to only the destination computer. It does

this by building a table of which computer is on which of its ports. This reduces network


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traffic significantly, especially on a network of more than 10 computers. It is not unusual

to find both hubs and switches on the same LAN.

Routers

Network routers are essentially very smart switches because they know about other LANs,

while switches only know about the network they are on. Routers connect LANs together,

sometimes across long distances, creating Wide Area Networks, or WANs. Routers are also

used to provide security on LANs by routing network traffic between LAN segments.

Network Software

All of the network components except the cabling have software that makes them work.

Network software is written to a set of standards that define the TCP/IP protocol suite. The

standard defines layers of software and how they talk with each other. Using the same set

of rules allows networking equipment from different vendors to work together, allowing

you to take advantage of the best equipment in each category.

Gateway:

A gateway is a piece of networking hardware used in telecommunications for

communications networks that allows data to flow from one discrete network to another.

Gateways are distinct from routers or switches in that they communicate using more than

one protocol and can operate at any of the 7 layers of the OSI model.

Advantages & Disadvantages of Gateways

A gateway is used to connect to two computers with different protocols in such a way that

they can communicate with one another. This is sometimes referred to as a communication

gateway. Gateways can be useful when attempting to connect computers with different

operating systems and functions, but can be difficult to troubleshoot.

A gateway can be used to connect computers with dissimilar protocols.

Flexibility

Some networks are set up through a router. A router can be used for computers with similar

protocols, meaning that they have similar hardware and software installed. A gateway

grants more flexibility for your network because it can translate information from

computers with different systems. This means that several different kinds of computers can

be set up on the same gateway, and the same information can be accessed from each

computer.


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Security

Gateways can also be programmed to grant or deny certain users privileges. Gateways also

allow for user authentication, so that a password or another form of security is necessary

before a user has access to the gateway. For networks which contain sensitive information,

this can be useful in ensuring that only privileged users have access to information. This

kind of security is featured on most networks and is integral to prevent unwanted access.

Time

Since a gateway must translate information from different protocols before passing it on,

there may be a time delay when using gateway networks. Instant transfer is almost never

possible when using gateways. A gateway may also deliver cached information, or old

information that is stored by the gateway, if the cache is not cleared properly. This can lead

to further time constraints when using gateways, as time must be taken to clear the cache.

Troubleshooting

A gateway follows a fairly rigid process and it therefore cannot be easily programmed.

Troubleshooting a gateway can be difficult as different tools are necessary for finding

problems on computers with different protocols. If a gateway fails, then communication

will be lost on the network. This communication cannot be restored until the problem is

located, which means going through each computer on the network and troubleshooting

them individually until the problem is found.


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UNIT-5

Microsoft Disk Operating System (MS-DOS)

The Microsoft Disk Operating System (MS-DOS) is an operating system developed for

PCs with x86 microprocessors. It is a command-line-based system, where all commands

are entered in text form and there is no graphical user interface.

MS-DOS was the most commonly used member of the family of disk operating systems.

It was the main choice as an operating system for IBM PC-compatible computer systems

during the 1980s to mid-1990s. MS-DOS was gradually replaced by systems with

graphical user interfaces, particularly Microsoft Windows.

MS-DOS was originally called 86-DOS. It was written by Tim Patterson (considered the

father of DOS) and owned by Seattle Computer Products. Microsoft bought 86DOS for

$75,000, licensed the software and released it with an IBM PC as MS-DOS

1.0 in 1982. MS-DOS was originally designed to run on any computer with an Intel 8086

processor, but the various hardware versions on these computers made compatibility

difficult. As a result, Microsoft provided hardware equipment manufacturers with a

development kit that could be used to tune the MS-DOS operating system for the

computer's specific hardware.

Features of DOS:

1. It is the primary system where the user will get an environment about the input and

output devices, e.g. Monitor, Keyboard, Printers etc.

2. It is helpful in performing file management e.g., creating, editing, deleting files etc.

3. It is a single user operating system. One user can operate at one time in this

operating system.

4. It is a character Based interface system. We can type letters or characters in this

operating system.

Drive Name: In computer data storage, drive letter assignment is the process of

assigning alphabetical identifiers to volumes. Unlike the concept of UNIX mount points,

where volumes are named and located arbitrarily in a single hierarchical namespace, drive

letter assignment allows multiple highest-level namespaces. Drive letter assignment is thus

a process of using letters to name the roots of the "forest" representing the file system; each

volume holds an independent "tree" (or, for non-hierarchical file systems, an independent

list of files).

File Allocation Table (FAT):A file allocation table (FAT) is a file system developed

for hard drives that originally used 12 or 16 bits for each cluster entry into the file allocation


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table. It is used by the operating system (OS) to manage files on hard drives and other

computer systems. It is often also found on in flash memory, digital cameras and portable

devices. It is used to store file information and extend the life of a hard drive.

Most hard drives require a process known as seeking; this is the actual physical searching

and positioning of the read/write head of the drive. The FAT file system was designed to

reduce the amount of seeking and thus minimize the wear and tear on the hard disc.

FAT was designed to support hard drives and subdirectories. The earlier FAT12 had a

cluster addresses to 12-bit values with up to 4078 clusters; it allowed up to 4084 clusters

with UNIX. The more efficient FAT16 increased to 16-bit cluster address allowing up to

65,517 clusters per volume, 512-byte clusters with 32MB of space, and had a larger file

system; with the four sectors it was 2,048 bytes.

File names and directory structure: A DOS file can have an 8 character name + an

optional 3 character extension. The extension is intended to indicate the 'type' of the file.

Most DOS and Windows programs assume some particular extension for the file they use;

Windows uses the extension to associate a particular program with a file.

The files are organized in a tree-structured directory. An arbitrary file is specified by a path,

device:\directory\directory\...\filename.ext

The special file name '.' refers to the current directory; the file name '..' refers to the parent

directory.

Long Windows file names, and file names containing blanks or certain special characters, are

mapped into MS-DOS file names of the form cccccc~1, cccccc~2, etc.

File naming rules – A file name has two parts primary name and extension. 8.3 file name

convention is used i.e. <8 characters for filename>.<3 chars for extension>. But special

characters cannot be used in file name as \ / : * ? ” <> |

8.3 filenames have at most eight characters, optionally followed by a period “.” and a filename

extension of at most three characters. For files with no extension, the “.” if present has no

significance (that is “myfile” and “myfile.” are equivalent). File and directory names are

uppercase, although systems that use the 8.3 standard are usually case-insensitive.


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VFAT, a variant of FAT with an extended directory format, was introduced in Windows 95

and Windows NT 3.5. It allowed mixed-case Unicode long filenames (LFNs) in addition to

classic 8.3 names.

To maintain backward-compatibility with legacy applications (on DOS and Windows

3.1), an 8.3 filename is automatically generated for every LFN, through which the file can

still be renamed, deleted or opened. The 8.3 filename can be obtained using the

Kernel32.dll function GetShortPathName.

MS-DOS boot process:

1. The BIOS, having completed its test and setup functions, loads the boot code found

in the master boot record and then transfers control of the system to it. At that point,

the master boot record code is executed. If the boot device is a floppy disk, the

process skips to step 7 below.

2. The next step in the process is the master boot code examining the master partition

table. It first must determine if there is an extended DOS partition, then it must

determine if there is a bootable partition specified in the partition table.

3. If the master boot code locates an extended partition on the disk, it loads the extended

partition table that describes the first logical volume in the extended partition. This

extended partition table is examined to see if it points to another extended partition

table. If it does, this second table is examined for information about the second logical

volume in the extended partition. Logical volumes in the extended partition have their

extended partition table chained together one to the next. This process continues until

all of the extended partitions have been loaded and recognized by the system.

4. Once the extended partition information (if any) has been loaded, the boot code

attempts to start the primary partition that is marked active, referred to as the boot

partition. If no boot partitions are marked active, then the boot process will terminate

with an error. The error message is often the same as that which occurs if the BIOS

could not locate a boot device, generally shown on screen as "No boot device", but

also can show up as "NO ROM BASIC - SYSTEM HALTED". If there is a primary

partition marked active and there is an installed operating system, the boot code will

boot it. The rest of the steps presume this example is of an MS- DOS primary

partition.


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5. At this stage, the master or volume boot sector is loaded into memory and tested, and

the boot code that it contains is given control of the remainder of the boot process.

6. The boot code examines the disk structures to ensure that everything is correct. If

not, the boot process will end in an error here.

7. During the next step, the boot code searches the root directory of the device being

booted for the operating system files that contain the operating system. For MSDOS,

these are the files "IO.SYS", "MSDOS.SYS" and "COMMAND.COM".

8. If no operating system files are found, the boot program will display an error message

similar to "Non-system disk or disk error - Replace and press any key when ready".

Keep in mind that his message does not means that the system was never booted. It

means that the BIOS examined the floppy disk for example and just rejected it

because it couldn't boot an operating system. The volume boot code was indeed

loaded and executed, as that is what posts the message when it can't find the operating

system files.

9. In the final stages of the boot process, presuming that the operating system files are

found, the boot program will load those operating system files into memory and

transfer control to them. In MS-DOS, the first is IO.SYS and its code is executed.

IO.SYS will then execute MSDOS.SYS. Then the more complete operating system

code loads and initializes the rest of the operating system structures beginning with

the command interpreter COMMAND.COM and then the execution of the

CONFIG.SYS and AUTOEXEC.BAT files. At this point the operating system code

itself has control of the computer.

MS-DOS system files

MS-DOS / PC DOS and some related disk operating systems use the files mentioned here.

System Files:

• IO.SYS (or IBMBIO.COM): This contains the system initialization code and built-in device

drivers.

• MSDOS.SYS (or IBMDOS.COM): This contains the DOS kernel.

Command line interpreter (Shell):

• COMMAND.COM: This is the command interpreter. User configuration files:

• AUTOEXEC.BAT: This is run by the default shell (usually COMMAND.COM) to execute

commands at startup.


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• CONFIG.SYS: This contains statements to configure DOS and load device drivers

DOS COMMANDS

INTERNAL COMMAND:An internal command is an MS-DOS command that is stored

in the system memory and loaded from the command.com or cmd.exe. The illustration

shows how commands contained within command.com are part of the command.com file.

However, with the external commands, each of the commands are their own separate file.

These commands are automatic loaded into the memory when operating system is loaded

into the memory. Thus these are also called memory-resident commands. The command

available are all combined together and are stored in Command.com file, which is a

executable command file. These internal command are further grouped according to their

properties. These are as follows.

General purpose File related commands Directory related commands

1. CLS

2. DIR

3. VER

4. VOL

5. DATE

6. TIME

7. COPYCON

8. TYPE

9. COPY

10. REN

11. DEL

12. MD

13. CD

14. RD

General purpose commands

1. CLS: - (Clear the screen) This command is used to clear the screen or wipe out everything

written on the screen. Syntax: - C:\> CLS and press Enter

2. DIR: - (Directory) Dir command is used for listing files and directories present in the current

disk.

Syntax:- C:\> DIR [/switches]

Example:- C:\> DIR /P


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Switches:-

/P Page wise

/W Widths wise

/S List all files and directory of subdirectories

/AH Display directory with hidden files

/AS Display directory with system files

/AD Display only directories present in current drive

3. VER :-( Version) Version numbers indicates that which edition of DOS we are working on.

Syntax:- C:\> VER press enter

Output:- C:\>VER

Windows 98 [Version 4.10.2222]

4. VOL:-(Volume) Displays the disk volume label and serial number, if it exist.

Syntax:- C:\> VOL press enter

Output:-C:\>VOL

Volume in drive C is JAI

Volume Serial Number is 3E42-1907

5. DATE:- Display the current Date

Syntax:- C:\> DATE

C:\>DATE


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Current date is Fri 02-15-2002 Enter

new date (mm-dd-yy):

Type DATE without parameters to display the current date setting and

a prompt for a new one. Press ENTER to keep the same date. Note: -

We enter new date in the format of MM-DD-YY.

6. TIME: - Display current time

Syntax:-C:\>TIME

C:\>TIME

Current time is 8:38:47.70a

Enter new time:

Type TIME with no parameters to display the current time setting and a prompt for a new one.

Press ENTER to keep the same time.

Note:- We enter the time in the format of 24 hour clock.

File related commands

7. COPY CON:- This command gives the facility to create a new text file.

Syntax:-C:\>COPYCON<Filename>

C:\>COPY CON Rose.txt

A clock in a office can never get stolen

Too many employees watch it all the time

^Z

1 file(s) copied

After copy con we must specify a suitable file name. Press enter. Start typing the

information’s of the file. After gathering the information we press ^Z (CTRL+Z) button or

F6 button to save the file. After pressing enter key computer will show a message like 1

file(s) copied. This means that file is stored in the disk. Suppose we don't want to save the

file or we just want to abort from file creation job, then we simply press ^C (CTRL+C)

button to abort without saving the file, intend of pressing ^Z button.

Notes:- 1. Never forget to give a suitable filename

2. You can use extension as .TXT for denoting the file as Text file.

8. TYPE:- This command is used to display the contents or text of any file to the display device.

Syntax:- C:\> TYPE <Filename>

A:\>TYPE GULAB.TXT


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A clock in an office can never get stolen

Too many employees watch it all the time

9. COPY: - Copy command is used for copy any file to another location or to copy the files

to another directory. This command may also be used for copying any file to another disk

with different file name.

Syntax: - C:\> COPY <Source filename><Target file name>

C:\>COPY ROSE.TXT ROSE.MSG

1 file(s) copied

TO copy a file from hard disk to floppy disk C:\>COPY

Rose.txt A:

1 file(s) copied

To copy a file from Floppy Disk to Hard disk

A:\>COPY LOTUS.TXT C:\

1 file(s) copied

10. REN:- (Rename) This command is used to change the name of any file or directory.

Syntax:- C:\> REN <Source filename><Target filename>

C:\>REN ROSE.TXT GULBAL.TXT

If we get successfully C:\ that means filename or directory name is get changed. Either it will

show the error message.

To changing the filename present in floppy disk

C:\>REN A:\ROSE.TXT GULAB.TXT

Note that you cannot specify a new drive or path for your destination.

11. DEL:- This command is used for erasing any file from the disk.

Syntax:- C:\> DEL <Filename>

C:\>DEL LOTUS.TXT

If it successfully erase the file from dosk then C:\> prompt will be appear, either computer

will show an error message.

Note:- /P option is used for permission before deleting the file.

Directory related commands

12. MD:- (Make Directory)- This command allows to create a new directory.

Syntax:- C:\> MD <Dirname>

C:\> MD REPORT

C:\>

Now this directory can be used for keeping various sort of reports. Under this directory we

can create another directory which is known as subdirectory.


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13. CD:- (Change Directory):- We can enter or exit from any directory using this command.

Syntax:- To access any directory

C:\> CD <Directory name>

C:\> CD REPORT

C:\REPORT>

Prompt will change with the directory name. If we keep two dots after CD command than we

will exit from the directory.

Syntax:-C:\> CD..

C:\REPORT> CD..

C:\>

14. RD:-(Remove directory):- This command is used when we want to remove any unusable

directory form our disk. Syntax:- C:\> RD <Directory name>

C:\> RD REPORT

15. PATH:- This command is used for display or sets directories for executable files. Syntax:-

C:\>PATH

This command display current path settings.

C:\>PATH=C:\WINDOWS\COMMAND;C:\WINDOWS\;C:\TC

This command will sets the directories windows, the command subfolder of windows and TC

folder for executable files. Operating system will look for executable files in these

directories.

NOTE:- If we need any help for above DOS commands the we put a '/?' symbol after

writing the command at DOS prompt . Example: - C:\> DIR/? Or C:\> COPY/?

External commands:

External commands are known as Disk residence commands. Because they can be store with

DOS directory or any disk which is used for getting these commands. Theses commands

help to perform some specific task. These are stored in a secondary storage device. Some

important external commands are given below-


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MORE MOVE FIND DOSKEY

MEM FC DISKCOPY FORMAT

SYS CHKDSK ATTRIB

XCOPY SORT LABEL

1. MORE:-Using TYPE command we can see the content of any file. But if length of file is

greater than 25 lines then remaining lines will scroll up. To overcome through this problem

we uses MORE command. Using this command we can pause the display after each 25

lines.

Syntax:- C:\> TYPE <File name> | MORE

C:\> TYPE ROSE.TXT | MORE or

C:\> DIR | MORE

2. MEM:-This command displays free and used amount of memory in the computer.

Syntax:- C:\> MEM the computer will display the

amount of memory.

3. SYS:- This command is used for copy system files to any disk. The disk having system

files are known as Bootable Disk, which are used for booting the computer.

Syntax:- C:\> SYS [Drive name] C:\> SYS

A:

System files transferred

This command will transfer the three main system files COMMAND.COM, IO.SYS,

MSDOS.SYS to the floppy disk.

4. XCOPY:- When we need to copy a directory instant of a file from one location to another

the we uses xcopy command. This command is much faster than copy command.

Syntax:- C:\> XCOPY < Source dirname > <Target dirname> C:\> XCOPY

TC TURBOC

5. MOVE:- Move command is used for moving one file or multiple files from one location

to another location or from one disk to another disk.

Syntax:- C:\> MOVE <file name> <path name>

C:\SONGS> MOVE *.MP3 C:\ SONGS\OLD SONGS\


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C:\>

6. FC:-(File Compare) This command is capable for comparing two set of files and display

difference between two files.

Syntax:- C:\> FC <First set of file> <Second set of file> C:\> FC

ROSE.TXT GULAB.TXT

7.CHKDSK:-(Check disk) - This command is used to check the status of a disk and show the

report of result status.

Syntax:- C:\> CHKDSK

C:\>CHKDSK

CHKDSK has NOT checked this drive for errors.

You must use SCANDISK to detect and fix errors on this drive.

Volume JAI created 10-19-2001 7:14p


4,203,073,536 bytes total disk space

381,988,864 bytes available on disk

4,096 bytes in each allocation unit

1,026,141 total allocation units on disk

93,259 available allocation units on disk

651,264 total bytes memory

610,784 bytes free

Instead of using CHKDSK, try using SCANDISK. SCANDISK can reliably detect and

fix a much wider range of disk problems.

8. SORT:- This command is useful when we want to sort a file. When we run this command

the result can be get to display device or file.

Syntax:- C:\> SORT /R < Input file name> <output file name>


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Suppose we have a file Player.txt which having the list of a cricket player team and we want to

sort the list of players, then we uses this command C:\> SORT Player.txt

If we not specify the output file name then result will show to the screen.

/R- switch is used for sorting the file in descending order like from Z to A or from 9 to 0.

9. FIND:- The FIND command is used to search a file for a text string.

Syntax:- C:\> FIND "String to search" <File name>

C:\TEST>find "office" gulab.txt

---------- gulab.txt

A clock in a office can never get stolen

10. DISKCOPY:- DISKCOPY copies the contents of a floppy disk to another.

Syntax:- C:\> DISKCOPY <Drive1> <Drive2> C:\> DISKCOPY

A: B:

This command will be copy all contents of A drive to B drive.

11. ATTRIB:- Sets the various type of attribute to a file. Like Read only, Archive, Hidden

and System attribute.

Syntax:- C:\> ATTRIB [± r] [± a] [± h] [± s] <File name> here r - for read only,

a- for archive, h - for hidden, s - for hidden attribute.

C:\> ATTRIB +r Gulab.txt

This command will change the attribute of file gulab.txt to read only mode. To remove

the read only attribute we will follow this command. C:\> ATTRIB -r Gulab.txt

12. LABEL:- If you are not happy with the volume label of hard disk, you can change it.

Syntax:- C:\> LABEL

C:\>LABEL

Volume in drive C is JAI


Volume label (11 characters, ENTER for none)? INFOWAY

13. DOSKEY:- Once we install doskey , our dos will star to memorize all commands we

uses. We can recall those commands using up or down arrow keys. It also gives the

facility to create macros, which creates a short key for long keyword or command.


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Key function for Doskey are given as-

UP, DOWN arrows recall commands

Esc clears current command

F7 displays command history

Alt+F7 clears command history

F9 selects a command by number

Alt+F10 clears macro definitions

Syntax:- C:\> DOSKEY DOSKey

installed

Creating Macros:- C:\>doskey

t=time

C:\>t

C:\>time

Current time is 3:39:05.97p Enter

new time:

To list out all macros defined just type DOSKEY/MACROS at dos prompt and press enter.

C:\>DOSKEY/MACROS

$D=date

T=time

14. FORMAT:- This command creates new Track & Sectors in a disk. Every

Syntax:- C:\> FORMAT [drive name] [/S]

C:\> FORMAT A: this command will create

new track & sectors. C:\> FORMAT A: /S

This command will transfer system files after formatting the disk.

Free and open source software (FOSS)

Free and open source software (FOSS), also known as free/liber open source software

(FLOSS) and free/open source software (F/OSS), is software developed by informal

collaborative networks of programmers. The source code is licensed free of charge,

encouraging modifications and improvements.


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The term free software refers to a lack of restrictions on individual users as well as zero

cost; the term open source software refers to collaborative or networked development.

FOSS, which embraces the benefits and adherents of both paradigms, is gaining widespread

acceptance as traditional modes of software design are challenged.

The increasing popularity of FOSS has led to frustration in some circles for at least three reasons:

Conventional software developers, distributors and sellers fear that FOSS will undercut their

profits.

Abuse of FOSS privileges may lead to questionable claims of copyright or trademark protection,

thereby spawning litigation.

The monetary value of FOSS is unclear, so governments have trouble figuring out how to tax

it.

Proprietary Software

Proprietary software is any software that is copyrighted and bears limits against use,

distribution and modification that are imposed by its publisher, vendor or developer.

Proprietary software remains the property of its owner/creator and is used by

endusers/organizations under predefined conditions.

Proprietary software may also be called closed-source software or commercial software.

Proprietary software is primarily commercial software that can be bought, leased or licensed

from its vendor/developer. In general, proprietary software doesn't provide end users or

subscribers with access to its source code. It can be purchased or licensed for a fee, but

relicensing, distribution or copying is prohibited. Most software is proprietary software and

is produced by an independent software vendor (ISV). The restrictions or conditions

imposed by the vendor/developer on proprietary software is elaborated within the software's

end-user license agreement (EULA), terms of service agreement (TOS) or other related use

agreements. The user/organization must accept the agreement prior to installing or using

the software. The software developer/vendor can take legal action against the end-

user/organization for violating the EULA or TOS.

Mobile Application (Mobile App)

A mobile application, most commonly referred to as an app, is a type of application software

designed to run on a mobile device, such as a smartphone or tablet computer. Mobile

applications frequently serve to provide users with similar services to those accessed on

PCs. Apps are generally small, individual software units with limited function. This use of

app software was originally popularized by Apple Inc. and its App Store, which offers

thousands of applications for the iPhone, iPad and iPod Touch.


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A mobile application also may be known as an app, web app, online app, iPhone app or

smartphone app.

Mobile applications are a move away from the integrated software systems generally found

on PCs. Instead, each app provides limited and isolated functionality such as a game,

calculator or mobile web browsing. Although applications may have avoided multitasking

because of the limited hardware resources of the early mobile devices, their specificity is

now part of their desirability because they allow consumers to hand-pick what their devices

are able to do.

The simplest mobile apps take PC-based applications and port them to a mobile device. As

mobile apps become more robust, this technique is somewhat lacking. A more sophisticated

approach involves developing specifically for the mobile environment, taking advantage of

both its limitations and advantages. For example, apps that use location-based features are

inherently built from the ground up with an eye to mobile given that the user does not have

the same concept of location on a PC.

Uses of Computers:

Computers have become an essential part of modern human life. Since the invention of computer

they have evolved in terms of increased computing power and decreased size.

Owing to the widespread use of computers in every sphere, Life in today’s world would be

unimaginable without computers. They have made human lives better and happier. There

are many computer uses in different fields of work. Engineers, architects, jewelers, and

filmmakers all use computers to design things. Teachers, writers, and most office workers

use computers for research, word processing and emailing. Small businesses can use

computers as a point of sale and for general record keeping.

Computers Aid at Education:

Computers have its dominant use in the education field which can significantly enhance

performance in learning. Even distance learning is made productive and effective through

internet and video-based classes. Researchers have massive usage of these computers in

their work from the starting to till the end of their scholarly work.

Computers in our Health and Medicine:

Most of the medical information can now be digitized from the prescription to reports.

Computation in the field of medicine allows us to offer varied miraculous therapies to the


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patients. ECG’s, radiotherapy wasn’t possible without computers. Aid of Computers at

Financial Institutions:

We know well that computers are being used by the financial institutions like banks for

different purposes. The foremost important thing is to store information about different

account holders in a database to be available at any time. Keeping the records of the cash

flow, giving the information regarding your account, Computers for our Pass time:

Computers are now the major entertainers and the primary pass time machines. We can use

computers for playing games, watching movies, listening to music, drawing pictures.

Computers are a part of our Transport System:

With internet on computers we can know the details of the buses or trains or the flight

available to our desired destination. The timings and even the updates on the delay can also

be known through these computers. We can book our tickets through online. Staff of the

transport system will keep a track of the passengers, trains or flight details, departure and

arrival timings by using computers.

Inevitable use of Computers in Business and Corporate Stages:

Every single information shared can be recorded by using computer. Official deals and the

issues were made even through online. We use email system to exchange the information.

It has wide uses in marketing, stock exchanges and bank. Even the departmental stores can’t

run effectively without computer.

Wonders of Computer in E-Commerce:

Electronic mail is the revolutionary service offered by the computes. Video Conferencing

is also another major advantage. Electronic shopping through online shopping added favor

to purchaser and merchants. Electronic banking is now at your hand where every bank has

online support for transaction of monetary issues. You can easily transfer your money

anywhere even from your home.

Computer at our Defense:

Computers are the main tools which help in developing missiles and other equipment in the

deference system. Designing and the maintenance are possible only through computers.

Computer builds the links between the soldiers and commanders through the satellite.

Construction of weapons and controlling their function is not possible without the aid of


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computers. The list of the criminals and the records of the cops are maintained regularly in

the system.

Computer is today’s Designer:

As per the title, computers aid in designing buildings, magazines, prints, newspapers, books

and many others. The construction layouts are designed beautifully on system using

different tools and software’s.

Linux

Linux is a free open source operating system (OS) based on UNIX that was created in 1991

by Linus Torvalds. Users can modify and create variations of the source code, known as

distributions, for computers and other devices. The most common use is as a server, but

Linux is also used in desktop computers, smartphones, e-book readers and gaming consoles,

etc.

A distribution of Linux includes the kernel (the central OS component and the bridge

between a software application and its data), system utilities, programs and tools for

downloading, installing and uninstalling OS updates.

History of Linux

The history of Linux began in 1991 with the commencement of a personal project by

Finnish student Linus Torvalds to create a new free operating system kernel. Since then, the

resulting Linux kernel has been marked by constant growth throughout its history. Since

the initial release of its source code in 1991, it has grown from a small number of C files

under a license prohibiting commercial distribution to the 4.15 version in 2018 with more

than 23.3 million lines of source code without commentsunder the GNU General Public

License v2. Features of Linux

Following are some of the important features of Linux Operating System.

• Portable − Portability means software can works on different types of hardware in same

way. Linux kernel and application programs supports their installation on any kind of

hardware platform.

• Open Source − Linux source code is freely available and it is community based

development project. Multiple teams work in collaboration to enhance the capability of

Linux operating system and it is continuously evolving.

• Multi-User − Linux is a multiuser system means multiple users can access system

resources like memory/ ram/ application programs at same time.

https://en.wikipedia.org/wiki/C_Programming_Language




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• Multiprogramming − Linux is a multiprogramming system means multiple applications

can run at same time.

• Hierarchical File System − Linux provides a standard file structure in which system files/

user files are arranged.

• Shell − Linux provides a special interpreter program which can be used to execute

commands of the operating system. It can be used to do various types of operations, call

application programs. etc.

• Security − Linux provides user security using authentication features like password

protection/ controlled access to specific files/ encryption of data.

Hardware Requirements of Linux:

Criteria Requirements

Operating System Linux 4 or 5 with the latest patches and upgrades

CPU Type Pentium 4 or higher; 2 GHz or higher

Memory/RAM 1 GB minimum, up to the system limit

Hard Disk 4 GB minimum

Other To run the Directory Server using port numbers less than 1024, such

as the default port 389, you must setup and start the Directory Server

as root, but it is not necessary to run the Directory Server as root.

Flavors of Linux

Even the smallest amount if research into Linux will have illustrated the sheer range of

distributions out there. They are all based on the original Linux kernel built by Linus

Torvalds (the father of modern Linux) and can all inter-operate to varying degrees. We have

large selection of Linux distros on CD and DVD.

a) Debian: - Debian is regarded as the largest Linux distribution to date in terms of

users. It is renowned for its stability and quality and its interoperability with other

software. It has a very large following and over 28,000 packages you can add to it. It

is very stable and newbie friendly. It just means that it is never the latest and greatest,

but is very, very stable. Currently on Debian Version 5, Lenny.


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b) Ubuntu: -Seemingly the most popular distro out in the world right now, since its

release five years ago. Some suggest it has as much as 40% of Linux desktops. It is

another good quality, stable release that is very newbie friendly. It even has a

migration assistant for Windows refugees. This eases the pain a little by helping you

in your first steps. Another distro that works with most hardware straight out of the

box. Current version 9.04 Jaunty Jackalope.

c) Fedora: -This is a distribution with a long history. Once part of Red Hat, Fedora was

launched for the ‘Linux Hobbyist’. It is very secure and has a large number of

packages available for it. This one seemed to be less newbie friendly than others,

with not so many options for desktop users. If you want to run a web server or

something then this would be ideal. Current version is Fedora 10, new version

shortly.

d) OpenSUSE: -This is another distro with a rich history, now owned by Novell. It is a

comprehensive package with some good documentation. The following is helpful

and informative and there are lots of packages available for it. Current release is 11.1.

e) Mandriva: -Mandriva used to be Mandrake, and even as a Windows user back then

I knew what that was. It is one of the distributions that offer both free and commercial

versions of the software. The commercial version is regarded as one of the best

distros for newbies. Although I don’t see that it has much that Ubuntu or Debian

doesn’t offer and for free. Current version is Mandriva 2009.1.

f) Slackware: -This is allegedly the oldest Linux distribution still around today. It is

supposed to be the cleanest and most bug free edition available, but seems quite hard

core. You definitely need skills to get into Slackware. It lags a little behind other

distributions and doesn’t have all the cool bits to make your desktop smart. Current

version 12.2.

g) FreeBSD: - It is primarily directed a server applications and is rated as one of the

most stable. It doesn’t have all the bells and whistles that some of the more popular

distros have but if you need something to run a server, you can’t go wrong with this.

Current version 7.2.

h) Mint: -It is based on Ubuntu, but is developed mainly ‘on demand’. The

programmers have forums and feedback loops which they subscribe to. They listen

and try to implement the best suggestions into the distribution. It has many specific


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tools, and to my mind is the most useable out of the box. Current version is Mint 6

Felicia.

i) PCLinuxOS: -Despite the not so catchy name this distribution is supposed to be very

good for the Linux newcomer. Another distro that works out of the box, natively

supporting lots of hardware. The documentation and website are pretty good if a little

disorganized. This one also seems to be English only, so if you speak something

other, then you had best look elsewhere. Current version is PCLinuxOS 2009.1

Linux Directory Structure (File System Structure) Explained with Examples:

The Linux file system structures and understand the meaning of individual high-level directories.


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1. / – Root


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Every single file and directory starts from the root directory.

Only root user has write privilege under this directory.

Please note that /root is root user’s home directory, which is not same as /.

2. /bin – User Binaries

Contains binary executable.

Common Linux commands you need to use in single-user modes are located under this directory.

Commands used by all the users of the system are located here.

For example: ps, ls, ping, grep, cp.

3. /sbin – System Binaries

Just like /bin, /sbin also contains binary executable.

But, the Linux commands located under this directory are used typically by system

administrator, for system maintenance purpose. For example: iptables, reboot,

fdisk, ifconfig, swapon

4. /etc – Configuration Files

Contains configuration files required by all programs.

This also contains startup and shutdown shell scripts used to start/stop individual programs.

For example: /etc/resolv.conf, /etc/logrotate.conf

5. /dev – Device Files Contains device files.

These include terminal devices, usb, or any device attached to the system.

For example: /dev/tty1, /dev/usbmon0

6. /proc – Process Information

Contains information about system process.

This is a pseudo filesystem contains information about running process. For example: /proc/{pid}

directory contains information about the process with that particular pid.

This is a virtual file system with text information about system resources. For example:

/proc/uptime


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7. /var – Variable Files var stands for variable files.

Content of the files that are expected to grow can be found under this directory.

This includes — system log files (/var/log); packages and database files (/var/lib); emails

(/var/mail); print queues (/var/spool); lock files (/var/lock); temp files needed across

reboots (/var/tmp);

8. /tmp – Temporary Files

Directory that contains temporary files created by system and users.

Files under this directory are deleted when system is rebooted.

9. /usr – User Programs

Contains binaries, libraries, documentation, and source-code for second level programs.

/usr/bin contains binary files for user programs. If you can’t find a user binary under /bin, look

under /usr/bin. For example: at, awk, cc, less, scp

/usr/sbin contains binary files for system administrators. If you can’t find a system binary under

/sbin, look under /usr/sbin. For example: atd, cron, sshd, useradd, userdel

/usr/lib contains libraries for /usr/bin and /usr/sbin

/usr/local contains users programs that you install from source. For example, when you install

apache from source, it goes under /usr/local/apache2

10. /home – Home Directories

Home directories for all users to store their personal files.

For example: /home/john, /home/nikita

11. /boot – Boot Loader Files

Contains boot loader related files.

Kernel initrd, vmlinux, grub files are located under /boot

For example: initrd.img-2.6.32-24-generic, vmlinuz-2.6.32-24-generic

12. /lib – System Libraries

Contains library files that supports the binaries located under /bin and /sbin

Library filenames are either ld* or lib*.so.*


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For example: ld-2.11.1.so, libncurses.so.5.7

13. /opt – Optional add-on Applications opt

stands for optional.

Contains add-on applications from individual vendors.

add-on applications should be installed under either /opt/ or /opt/ sub-directory.

14. /mnt – Mount Directory

Temporary mount directory where sysadmins can mount filesystems.

15. /media – Removable Media Devices

Temporary mount directory for removable devices.

For examples, /media/cdrom for CD-ROM; /media/floppy for floppy drives; /media/cdrecorder

for CD writer

16. /srv – Service Data srv stands for service.

Contains server specific services related data.

For example, /srv/cvs contains CVS related data.

Function of Profile and Login Files in Linux: -

On LINUX like systems, everything runs off a shell. A shell/terminal/command line is what

runs every program on *NIX systems. When the user first logs in, there is a shell that is first

launched then the login manager is executed inside that shell. This shell that is invoked at

the time of login is called login shell.

Login shell is the parent process. After you login, everything that you see, the graphics the

UI, and all the programs that you start will naturally be child processes of the login manager

which in turn is a child process of a login shell.

When a Bourne compatible login shell starts, it first sources (parse & execute) the system

wide files like /etc./profile. Then it sources the user specific initialization file. Every user

specific file resides in the particular user’s home directory which in most cases is

/home/<user>/. So the file that login shell will source for user specific initialization is

~/.profile (~ is a shorthand for home directory).


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The original Bourne shell was just called sh. Now, there are many Bourne compatible shells

like the most famous is bash, another awesome shell is zsh. So this applies to all sh

compatible shells, they first source /etc/profile, then their own systemwide config (like

/etc/bashrc or /etc/zshrc) then for user specific init they source ~/.profile then they source

their own login configs (~/.bash_profile or ~/.zprofile).

Linux Kernel: -

Kernel is the core part of Linux. It is responsible for all major activities of this operating

system. It consists of various modules and it interacts directly with the underlying hardware.

Kernel provides the required abstraction to hide low level hardware details to system or

application programs.

A kernel is the lowest level of easily replaceable software that interfaces with the hardware

in your computer. It is responsible for interfacing all of your applications that are running

in “user mode” down to the physical hardware, and allowing processes, known as servers,

to get information from each other using inter-process communication (IPC).

Different Types of Kernels There are, of course, different ways to build a kernel and architectural considerations when

building one from scratch. In general, most kernels fall into one of three types: monolithic,

microkernel, and hybrid. Linux is a monolithic kernel while OS X (XNU) and Windows 7

use hybrid kernels. Let’s take a quick tour of the three categories so we can go into more

detail later.

Microkernel: A microkernel takes the approach of only managing what it has to: CPU, memory, and IPC.

Pretty much everything else in a computer can be seen as an accessory and can be handled

in user mode. Microkernels have a advantage of portability because they don’t have to

worry if you change your video card or even your operating system so long as the operating

system still tries to access the hardware in the same way. Microkernels also have a very

small footprint, for both memory and install space, and they tend to be more secure because

only specific processes run in user mode which doesn’t have the high permissions as

supervisor mode. Pros Portability

• Small install footprint

• Small memory footprint

• Security Cons

• Hardware is more abstracted through drivers

• Hardware may react slower because drivers are in user mode Processes have to wait in

a queue to get information


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• Processes can’t get access to other processes without waiting

Monolithic Kernel:

Monolithic kernels are the opposite of microkernels because they encompass not only the

CPU, memory, and IPC, but they also include things like device drivers, file system

management, and system server calls. Monolithic kernels tend to be better at accessing

hardware and multitasking because if a program needs to get information from memory or

another process running it has a more direct line to access it and doesn’t have to wait in a

queue to get things done. This however can cause problems because the more things that

run in supervisor mode, the more things that can bring down your system if one doesn’t

behave properly. Pros

• More direct access to hardware for programs

• Easier for processes to communicate between eachother

• If your device is supported, it should work with no additional installations Processes

react faster because there isn’t a queue for processor time Cons

• Large install footprint

• Large memory footprint

• Less secure because everything runs in supervisor mode

Hybrid Kernel:

Hybrid kernels have the ability to pick and choose what they want to run in user mode and

what they want to run in supervisor mode. Often times things like device drivers and

filesystem I/O will be run in user mode while IPC and server calls will be kept in the

supervisor mode. This give the best of both worlds but often will require more work of the

hardware manufacturer because all of the driver responsibility is up to them. It also can

have some of the latency problems that is inherent with microkernels. Pros

• Developer can pick and choose what runs in user mode and what runs in supervisor mode

• Smaller install footprint than monolithic kernel

• More flexible than other models Cons

• Can suffer from same process lag as microkernel


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• Device drivers need to be managed by user (typically)

Where Are the Linux Kernel Files?

The kernel file, in Ubuntu, is stored in your /boot folder and is called vmlinuz-version. The

name vmlinuz comes from the unix world where they used to call their kernels simply

“unix” back in the 60’s so Linux started calling their kernel “linux” when it was first

developed in the 90’s.

When virtual memory was developed for easier multitasking abilities, “vm” was put at the

front of the file to show that the kernel supports virtual memory. For a while the Linux

kernel was called vmlinux, but the kernel grew too large to fit in the available boot memory

so the kernel image was compressed and the ending x was changed to a z to show it was

compressed with zlib compression. This same compression isn’t always used, often

replaced with LZMA or BZIP2, and some kernels are simply called zImage. The version

numbering will be in the format A.B.C.D where A.B will probably be 2.6, C will be your

version, and D indicates your patches or fixes.

In the /boot folder there will also be other very important files called initrd.img-version,

system.map-version, and config-version. The initrd file is used as a small RAM disk that

extracts and executes the actual kernel file. The system.map file is used for memory

management before the kernel fully loads, and the config file tells the kernel what options

and modules to load into the kernel image when the it is being compiled.

Linux Kernel Architecture


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Because the Linux kernel is monolithic, it has the largest footprint and the most complexity

over the other types of kernels. This was a design feature which was under quite a bit of

debate in the early days of Linux and still carries some of the same design flaws that

monolithic kernels are inherent to have.

One thing that the Linux kernel developers did to get around these flaws was to make kernel

modules that could be loaded and unloaded at runtime, meaning you can add or remove

features of your kernel on the fly. This can go beyond just adding hardware functionality to

the kernel, by including modules that run server processes, like low level virtualization, but

it can also allow the entire kernel to be replaced without needing to reboot your computer

in some instances.

Imagine if you could upgrade to a Windows service pack without ever needing to reboot…

Kernel Modules

What if Windows had every driver available already installed and you just had to turn on

the drivers you needed? That is essentially what kernel modules do for Linux. Kernel

modules, also known as a loadable kernel module (LKM), are essential to keeping the kernel

functioning with all of your hardware without consuming all of your available memory.

A module typically adds functionality to the base kernel for things like devices, file systems,

and system calls. LKMs have the file extension .ko and are typically stored in the

/lib/modules directory. Because of their modular nature you can easily customize your

kernelby setting modules to load, or not load, during startup with the menuconfig command

or by editing your /boot/config file, or you can load and unload modules on the fly with the

modprobe command.

Linux Commands

1. File Commands

(i) File Administration

ls [option(s)] [file(s)]

If you run ls without any additional parameters, the program will list the contents of the current

directory in short form.


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-l

Detailed list

-a

Displays hidden files

cp [option(s)] sourcefile targetfile Copies

sourcefile to targetfile.

-i

Waits for confirmation, if necessary, before an existing targetfile is overwritten

-r

Copies recursively (includes subdirectories) mv

[option(s)] sourcefile targetfile

Copies sourcefile to targetfile then deletes the original sourcefile.

-b

Creates a backup copy of the sourcefile before moving

-i

Waits for confirmation, if necessary, before an existing targetfile is overwritten rm

[option(s)] file(s)

Removes the specified files from the file system. Directories are not removed by rm unless

the option -r is used.

-r

Deletes any existing subdirectories -i

Waits for confirmation before deleting each file. ln

[option(s)] sourcefile targetfile

Creates an internal link from the sourcefile to the targetfile, under a different name.

Normally, such a link points directly to the sourcefile on one and the same file system.

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However, if ln is executed with the -s option, it creates a symbolic link that only points to

the directory where the sourcefile is located, thus enabling linking across file systems. -s

Creates a symbolic link cd

[options(s)] [directory]

Changes the current directory. cd without any parameters changes to the user's home directory.

mkdir [option(s)] directoryname Creates

a new directory.

rmdir [option(s)] directoryname

Deletes the specified directory, provided it is already empty. chown

[option(s)] username.group file(s)

Transfers the ownership of a file to the user with the specified user name.

-R

Changes files and directories in all subdirectories. chgrp

[option(s)] groupname file(s)

Transfers the group ownership of a given file to the group with the specified group name. The

file owner can only change group ownership if a member of both the existing and the new

group.

chmod [options] mode file(s) Changes

the access permissions.

The mode parameter has three parts: group, access, and access type. group accepts the following

characters:

u user

g

group

o

others


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For access, access is granted by the + symbol and denied by the - symbol.

The access type is controlled by the following options: r

read w

write

x

eXecu

te —

execut

ing

files

or

changi

ng to

the

direct

ory. s

Set uid bit — the application or program is started as if it were started by the owner of the file.

gzip [parameters] file(s)

This program compresses the contents of files, using complex mathematical algorithms.

Files compressed in this way are given the extension .gz and need to be uncompressed

before they can be used. To compress several files or even entire directories, use the tar

command.

-d decompresses the packed gzip files so they return to their original size and can be

processed normally (like the command gunzip).

tar options archive file(s)

The tar puts one file or (usually) several files into an archive. Compression is optional.


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tar is a quite complex command with a number of options available. The most frequently used

options are:

-f

Writes the output to a file and not to the screen as is usually the case -c

Creates a new tar archive

-r

Adds files to an existing archive

-t

Outputs the contents of an archive

-u

Adds files, but only if they are newer than the files already contained in the archive

-x

Unpacks files from an archive (extraction)

-z

Packs the resulting archive with gzip

-j

Compresses the resulting archive with bzip2

-v

Lists files processed

The archive files created by tar end with .tar. If the tar archive was also compressed using gzip,

the ending is .tgz or .tar.gz. If it was compressed using bzip2, .tar.bz2.

Application examples can be found in Section “Archives and Data Compression”.

locate pattern(s)

The locate command can find in which directory a specified file is located. If desired, use

wild cards to specify file names. The program is very speedy, as it uses a database

specifically created for the purpose (rather than searching through the entire file system).

This very fact, however, also results in a major drawback: locate is unable to find any files

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created after the latest update of its database. The database can be generated by root with

updatedb. updatedb [options(s)]

This command performs an update of the database used by locate. To include files in all

existing directories, run the program as root. It also makes sense to place it in the

background by appending an ampersand (&), so you can immediately continue working on

the same command line (updatedb &).

find [option(s)]

The find command allows you to search for a file in a given directory. The first argument

specifies the directory in which to start the search. The option -name must be followed by

a search string, which may also include wild cards. Unlike locate, which uses a database,

find scans the actual directory.

Commands to Access File Contents

cat [option(s)] file(s)

The cat command displays the contents of a file, printing the entire contents to the screen without

interruption.

-n

Numbers the output on the left margin less

[option(s)] file(s)

This command can be used to browse the contents of the specified file. Scroll half a screen

page up or down with PgUp and PgDn or a full screen page down with Space. Jump to the

beginning or end of a file using Home and End. Press Q to exit the program. grep

[option(s)] searchstring filenames

The grep command finds a specific searchstring in the specified file(s). If the search string

is found, the command displays the line in which the searchstring was found along with the

file name.

-i

Ignores case

-l

Only displays the names of the respective files, but not the text lines -n

Additionally displays the numbers of the lines in which it found a hit





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-l

Only lists the files in which searchstring does not occur diff

[option(s)] file1 file2

The diff command compares the contents of any two files. The output produced by the program

lists all lines that do not match.

This is frequently used by programmers who need only send their program alterations and not

the entire source code.

-q

Only reports whether the two given files differ

File Systems

mount [option(s)] [<device>] mountpoint

This command can be used to mount any data media, such as hard disks, CD-ROM drives, and

other drives, to a directory of the Linux file system.

-r

mount read-only

-t filesystem

Specifies the file system. The most common are ext2 for Linux hard disks, msdos for MS-DOS

media, vfat for the Windows file system, and iso9660 for CDs.

For hard disks not defined in the file /etc/fstab, the device type must also be specified umount

[option(s)] mountpoint

This command unmounts a mounted drive from the file system. To prevent data loss, run

this command before taking a removable data medium from its drive. Normally, only root

is allowed to run the commands mount and umount. To enable other users to run these

commands, edit the /etc/fstab file to specify the option user for the respective drive.

2. System Commands

System Information df [option(s)]

[directory]


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The df (disk free) command, when used without any options, displays information about

the total disk space, the disk space currently in use, and the free space on all the mounted

drives. If a directory is specified, the information is limited to the drive on which that

directory is located.

-H shows the number of occupied blocks in gigabytes, megabytes, or kilobytes — in

humanreadable format

-t

Type of file system (ext2, nfs, etc.) du

[option(s)] [path]

This command, when executed without any parameters, shows the total disk space occupied by

files and subdirectories in the current directory.

-a

Displays the size of each individual file

-h

Output in human-readable form

-s

Displays only the calculated total size free

[option(s)]

The command free displays information about RAM and swap space usage, showing the total

and the used amount in both categories.

-b

Output in bytes

-k

Output in kilobytes

-m

Output in megabytes date

[option(s)]


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This simple program displays the current system time. If run as root, it can also be used to

change the system time. Details about the program are available in date. Processes top

[options(s)] top provides a quick overview of the currently running processes. Press H to

access a page that briefly explains the main options to customize the program.

ps [option(s)] [process ID]

If run without any options, this command displays a table of all your own programs or

processes — those you started. The options for this command are not preceded by hyphen.

aux

Displays a detailed list of all processes, independent of the owner.

kill [option(s)] process ID

Unfortunately, sometimes a program cannot be terminated in the normal way. However, in

most cases, you should still be able to stop such a runaway program by executing the kill

command, specifying the respective process ID (see top and ps).

kill sends a TERM signal that instructs the program to shut itself down. If this does not help, the

following parameter can be used:

-9

Sends a KILL signal instead of a TERM signal, with which the process really is annihilated

by the operating system. This brings the specific processes to an end in almost all cases.

killall [option(s)] processname

This command is similar to kill, but uses the process name (instead of the process ID) as an

argument, causing all processes with that name to be killed. Network

ping [option(s)] host name|IP address

The ping command is the standard tool for testing the basic functionality of TCP/IP

networks. It sends a small data packet to the destination host, requesting an immediate reply.

If this works, pingdisplays a message to that effect, which indicates that the network link is

basically functioning.

-c number Determines the total number of packages to send and ends after they have been

dispatched. By default, there is no limitation set.

-f

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flood ping: sends as many data packages as possible. A popular means, reserved to root, to

test networks.

-i

value Specifies the interval between two data packages in seconds. Default: one second nslookup

The Domain Name System resolves domain names to IP addresses. With this tool, send queries

to information servers (DNS servers).

telnet [option(s)] host name or IP address

Telnet is actually an Internet protocol that enables you to work on remote hosts across a

network. telnet is also the name of a Linux program that uses this protocol to enable

operations on remote computers.

Warning

Do not use telnet over a network on which third parties can eavesdrop. Particularly on the

Internet, use encrypted transfer methods, such as ssh, to avoid the risk of malicious misuse

of a password (see the man page for ssh). Miscellaneous

passwd [option(s)] [username]

Users may change their own passwords at any time using this command. Furthermore, the

administrator root can use the command to change the password of any user on the system.

su [option(s)] [username]

The su command makes it possible to log in under a different user name from a running

session. When using the command without specifying a user name, you will be prompted

for the root password. Specify a user name and the corresponding password to use the

environment of the respective user. The password is not required from root, as root is

authorized to assume the identity of any user.

halt [option(s)]

To avoid loss of data, you should always use this program to shut down your system.

reboot [option(s)]

Does the same as halt with the difference that the system performs an immediate reboot.

clear

This command cleans up the visible area of the console. It has no options.

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