SubjectCode: U16CA1A1 GOVERNMENT ARTS COLLEGE ...

1

SubjectCode: U16CA1A1

GOVERNMENT ARTS COLLEGE (AUTONOMOUS), KARUR-05B.Com. (CA) -

I SEMESTER – FIRST ALLIED COURSE - I

INTRODUCTION TO INFORMATION TECHNOLOGY

STUDY MATERIAL PREPARED BY

S.SARANYA

GUEST LECTURER

PG AND RESEARCH DEPARTMENT OF COMMERCE

GOVT. ARTS COLLEGE (AUTONOMOUS), KARUR -5.

2

UNIT - I

Introduction to Computers

Computer: is an electronic device that operates (works) under the control of programs

stored in its own memory unit. A computer is an electronic machine that processes raw data

to give information as output.

An electronic device that accepts data as input, and transforms it under the influence

of a set of special instructions called Programs, to produce the desired output (referred to as

Information).

Characteristics / Features of a Computer

Before 20th century, most information was processed manually or by use of simple

machines. Today, millions of people are using computers in offices and at home to produce

and store all types of information. The following are some of the attributes that make

computers widely accepted & used in the day-to-day activities in our society:

1. Speed:

Computers operate at very high speeds, and can perform very many functions within a

very short time.They can perform a much-complicated task much faster than a human

being.The speed of a computer is measured in Fractions of seconds.

Millisecond - a thousandth of a second (10-3)

Microsecond - a millionth of a second (10-6)

Nanosecond - a thousand millionth of a second (10-9)

Picosecond - a million millionth of a second (10-12)

The speed of a computer is usually linked to the technology used to build it.

2. Accuracy:

Unlike human beings, computers are very accurate, i.e., they never make mistakes.A

computer can work for very long periods without going wrong. However, when an error

occurs the computer has a number of in-built, self-checking features in their electronic

components that can detect & correct such errors.

3

Usually errors are committed by the users entering the data to the computer, thus the

saying Garbage in Garbage Out (GIGO).This means that, if you enter incorrect data into the

computer and have it processed, the computer will give you misleading information.

3. Reliability.

The computer can be relied upon to produce the correct answer if it is given the

correct instructions & supplied with the correct data.Therefore, if you want to add two

numbers, but by mistake, give the computer a “Multiply” instruction, the computer will not

know that you intended to “ADD”; it will multiply the numbers supplied.Similarly, if you

give it the ADD instruction, but make a mistake and enter an incorrect data; let say, 14 & 83

instead of 14 & 38; then the computer will produce the “wrong” answer 97 instead of 52.

However, note that, 97 is ‘correct’ based on the data supplied.Therefore, the output produced

by a computer is only as reliable as the instructions used & the data supplied.

4. Consistency:

Computers are usually consistent. This means that, given the same data & the same

instructions, they will produce the same answer every time that particular process is repeated.

5. Storage:

­ A computer is capable of storing large amounts of data or instructions in a very

small space.

­ A computer can store data & instructions for later use, and it can produce/ retrieve

this data when required so that the user can make use of it.

­ Data stored in a computer can be protected from unauthorized individuals through

the use of passwords.

6. Diligence:

Unlike human beings, a computer can work continuously without getting tired or

bored. Even if it has to do a million calculations, it will do the last one with the same speed

and accuracy as the first one.

7. Automation:

A computer is an automatic device. This is because, once given the instructions, it is

guided by these instructions and can carry on its job automatically until it is complete.It can

also perform a variety of jobs as long as there is a well-defined procedure.

8. Versatile:

A computer can be used in different places to perform a large number of different jobs

depending on the instructions fed to it.

9. Imposition of a formal approach to working methods:

Because a computer can only work with a strict set of instructions, it identifies and

imposes rigid rules for dealing with the data it is given to process.

4

HISTORY OF COMPUTER

The first counting device was used by the primitive people. They used sticks, stones

and bones as counting tools. As human mind and technology improved with time more

computing devices were developed. Some of the popular computing devices starting with the

first to recent ones are described below;

Abacus

The history of computer begins with the birth of abacus which is believed to be the

first computer. It is said that Chinese invented Abacus around 4,000 years ago.It was a

wooden rack which has metal rods with beads mounted on them. The beads were moved by

the abacus operator according to some rules to perform arithmetic calculations. Abacus is still

used in some countries like China, Russia and Japan.

Napier's Bones

It was a manually-operated calculating device which was invented by John Napier

(1550-1617) of Merchiston. In this calculating tool, he used 9 different ivory strips or bones

marked with numbers to multiply and divide. So, the tool became known as "Napier's Bones.

It was also the first machine to use the decimal point.

Pascaline

Pascaline is also known as Arithmetic Machine or Adding Machine. It was invented

between 1642 and 1644 by a French mathematician-philosopher Biaise Pascal. It is believed

that it was the first mechanical and automatic calculator.Pascal invented this machine to help

his father, a tax accountant. It could only perform addition and subtraction. It was a wooden

box with a series of gears and wheels. When a wheel is rotated one revolution, it rotates the

neighboring wheel. A series of windows is given on the top of the wheels to read the totals.

Stepped Reckoner or Leibnitz wheel

It was developed by a German mathematician-philosopher Gottfried Wilhelm

Leibnitz in 1673. He improved Pascal's invention to develop this machine. It was a digital

mechanical calculator which was called the stepped reckoner as instead of gears it was made

of fluted drums.

Difference Engine

In the early 1820s, it was designed by Charles Babbage who is known as "Father of

Modern Computer". It was a mechanical computer which could perform simple calculations.

It was a steam driven calculating machine designed to solve tables of numbers like logarithm

tables.

Analytical Engine

This calculating machine was also developed by Charles Babbage in 1830. It was a

mechanical computer that used punch-cards as input. It was capable of solving any

mathematical problem and storing information as a permanent memory.

5

Tabulating Machine

It was invented in 1890, by Herman Hollerith, an American statistician. It was a

mechanical tabulator based on punch cards. It could tabulate statistics and record or sort data

or information. This machine was used in the 1890 U.S. Census. Hollerith also started the

Hollerith?s Tabulating Machine Company which later became International Business

Machine (IBM) in 1924.

Differential Analyzer

It was the first electronic computer introduced in the United States in 1930. It was an

analog device invented by Vannevar Bush. This machine has vacuum tubes to switch

electrical signals to perform calculations. It could do 25 calculations in few minutes.

Mark I

The next major changes in the history of computer began in 1937 when Howard

Aiken planned to develop a machine that could perform calculations involving large

numbers. In 1944, Mark I computer was built as a partnership between IBM and Harvard. It

was the first programmable digital computer.

GENERATIONS OF COMPUTERS

A generation of computers refers to the specific improvements in computer

technology with time. In 1946, electronic pathways called circuits were developed to perform

the counting. It replaced the gears and other mechanical parts used for counting in previous

computing machines.

In each new generation, the circuits became smaller and more advanced than the

previous generation circuits. The miniaturization helped increase the speed, memory and

power of computers. There are five generations of computers which are described below;

First Generation Computers

The first generation (1946-1959) computers were slow, huge and expensive. In these

computers, vacuum tubes were used as the basic components of CPU and memory. These

computers were mainly depended on batch operating system and punch cards. Magnetic tape

and paper tape were used as output and input devices in this generation;

Some of the popular first generation computers are;

o ENIAC ( Electronic Numerical Integrator and Computer)

o EDVAC ( Electronic Discrete Variable Automatic Computer)

o UNIVACI( Universal Automatic Computer)

Second Generation Computers

The second generation (1959-1965) was the era of the transistor computers. These

computers used transistors which were cheap, compact and consuming less power; it made

transistor computers faster than the first generation computers.

6

In this generation, magnetic cores were used as the primary memory and magnetic

disc and tapes were used as the secondary storage. Assembly language and programming

languages like COBOL and FORTRAN, and Batch processing and multiprogramming

operating systems were used in these computers.

Some of the popular second generation computers are;

o IBM 1620

o IBM 7094

o CDC 1604

Third Generation Computers

The third generation computers used integrated circuits (ICs) instead of transistors. A

single IC can pack huge number of transistors which increased the power of a computer and

reduced the cost. The computers also became more reliable, efficient and smaller in size.

These generation computers used remote processing, time-sharing, multi programming as

operating system. Also, the high-level programming languages like FORTRON-II TO IV,

COBOL, PASCAL PL/1, ALGOL-68 were used in this generation.

Some of the popular third generation computers are;

o IBM-360 series

o Honeywell-6000 series

o PDP(Personal Data Processor)

Fourth Generation Computers

The fourth generation (1971-1980) computers used very large scale integrated (VLSI)

circuits; a chip containing millions of transistors and other circuit elements. These chips made

this generation computers more compact, powerful, fast and affordable. These generation

computers used real time, time sharing and distributed operating system. The programming

languages like C, C++, DBASE were also used in this generation.

Some of the popular fourth generation computers are;

o DEC 10

o STAR 1000

o PDP 11

o CRAY-1(Super Computer)

Fifth Generation Computers

In fifth generation (1980-till date) computers, the VLSI technology was replaced with

ULSI (Ultra Large Scale Integration). It made possible the production of microprocessor

chips with ten million electronic components. This generation computers used parallel

processing hardware and AI (Artificial Intelligence) software. The programming languages

used in this generation were C, C++, Java, .Net, etc.

Some of the popular fifth generation computers are;

7

o Desktop

o Laptop

o NoteBook

o UltraBook

o ChromeBook

TYPES OF COMPUTER

We can categorize computer in two ways: on the basis of data handling capabilities

and size.On the basis of data handling capabilities, the computer is of three types:

o Analogue Computer

o Digital Computer

o Hybrid Computer

1) Analogue Computer

Analogue computers are designed to process analogue data. Analogue data is

continuous data that changes continuously and cannot have discrete values. We can say that

analogue computers are used where we don't need exact values always such as speed,

temperature, pressure and current.Analogue computers directly accept the data from the

measuring device without first converting it into numbers and codes.

Speedometer and mercury thermometer are examples of analogue computers.

Advantages of using analogue computers:

o It allows real-time operations and computation at the same time and continuous

representation of all data within the rage of the analogue machine.

o In some applications, it allows performing calculations without taking the help of

transducers for converting the inputs or outputs to digital electronic form and vice

versa.

o The programmer can scale the problem for the dynamic range of the analogue

computer. It provides insight into the problem and helps understand the errors and

their effects.

Types of analogue computers:

Slide Rules:

Differential Analysers

Castle Clock

Electronic Analogue Computer

2) Digital Computer

Digital computer is designed to perform calculations and logical operations at high

speed. It accepts the raw data as input in the form of digits or binary numbers (0 and 1) and

processes it with programs stored in its memory to produce the output. All modern computers

8

like laptops, desktops including smartphones that we use at home or office are digital

computers.

Advantages of digital computers:

o It allows you to store a large amount of information and to retrieve it easily whenever

you need it.

o You can easily add new features to digital systems more easily.

o The cost of hardware is less due to the advancement in the IC technology.

o It offers high speed as the data is processed digitally.

o It is highly reliable as it uses error correction codes.

3) Hybrid Computer

Hybrid computer has features of both analogue and digital computer. It is fast like an

analogue computer and has memory and accuracy like digital computers. It can process both

continuous and discrete data. It accepts analogue signals and convert them into digital form

before processing. So, it is widely used in specialized applications where both analogue and

digital data is processed. For example, a processor is used in petrol pumps that converts the

measurements of fuel flow into quantity and price. Similarly, they are used in airplanes,

hospitals, and scientific applications.

Advantages of using hybrid computers:

o Its computing speed is very high due to the all-parallel configuration of the analogue

subsystem.

o It produces precise and quick results that are more accurate and useful.

o It has the ability to solve and manage big equation in real-time.

o It helps in the on-line data processing.

On the basis of size, the computer can be of five types:

1) Supercomputer

Supercomputers are the biggest and fastest computers. They are designed to process

huge amount of data. A supercomputer can process trillions of instructions in a second. It

has thousands of interconnected processors.Supercomputers are particularly used in scientific

and engineering applications such as weather forecasting, scientific simulations and nuclear

energy research. The first supercomputer was developed by Roger Cray in 1976.

Characteristics or applications of supercomputers:

o It has the ability to decrypt your password to enhance protection for security reasons.

o It produces excellent results in animations.

o It is used for virtual testing of nuclear weapons and critical medical tests.

o It helps in designing the flight simulators for pilots at the beginner level for their

training.

o It helps in extracting useful information from data storage centres or cloud system.

For example, in insurance companies.

2) Mainframe computer

9

Mainframe computers are designed to support hundreds or thousands of users

simultaneously. They can support multiple programs at the same time. It means they can

execute different processes simultaneously. These features of mainframe computers make

them ideal for big organizations like banking and telecom sectors, which need to manage and

process high volume of data.Mainframe computers are designed to support hundreds or

thousands of users simultaneously. They can support multiple programs at the same time. It

means they can execute different processes simultaneously.

Characteristics of Mainframe Computers:

o It can process huge amount of data, e.g. millions of transactions in a second in the

banking sector.

o It has a very long life. It can run smoothly for up to 50 years after proper installation.

o It gives excellent performance with large scale memory management.

o It has the ability to share or distribute its workload among other processors and

input/output terminals.

3) Miniframe or Minicomputer

It is a midsize multiprocessing computer. It consists of two or more processors and

can support 4 to 200 users at one time. Miniframe computers are used in institutes and

departments for tasks such as billing, accounting and inventory management. A

minicomputer lies between the mainframe and microcomputer as it is smaller than

mainframe but larger than a microcomputer.

Characteristics of miniframe or minicomputer:

o It is light weight that makes it easy to carry and fit anywhere.

o It is less expensive than mainframe computers.

o It is very fast compared to its size.

o It remains charged for a long time.

o It does not require a controlled operational environment.

4) Workstation

Workstation is a single user computer that is designed for technical or scientific

applications. It has a faster microprocessor, a large amount of RAM and high speed graphic

adapters. It generally performs a specific job with great expertise; accordingly, they are of

different types such as graphics workstation, music workstation and engineering design

workstation.

Characteristics of workstation computer:

o It is a high-performance computer system designed for a single user for business or

professional use.

o It has larger storage capacity, better graphics, and more powerful CPU than a personal

computer.

o It can handle animation, data analysis, CAD, audio and video creation and editing.

10

5) Microcomputer

Microcomputer is also known as a personal computer. It is a general-purpose

computer that is designed for individual use. It has a microprocessor as a central processing

unit, memory, storage area, input unit and output unit. Laptops and desktop computers are

examples of microcomputers. They are suitable for personal work that may be making an

assignment, watching a movie, or at office for office work.

Characteristics of a microcomputer:

o It is the smallest in size among all types of computers.

o A limited number of software can be used.

o It is designed for personal work and applications. Only one user can work at a time.

o It is less expansive and easy to use.

o It does not require the user to have special skills or training to use it.

o Generally, comes with single semiconductor chip.

o It is capable of multitasking such as printing, scanning, browsing, watching videos,

etc.

COMPONENTS OF COMPUTER HARDWARE

There are 5 main computer components that are given below:

o Input Devices

o CPU

o Output Devices

o Primary Memory

o Secondary Memory

The operations of computer components are given below:

1) Inputting: It is the process of entering raw data, instructions and information into the

computer. It is performed with the help of input devices.

2) Storing: The computer has primary memory and secondary storage to store data and

instructions. It stores the data before sending it to CPU for processing and also stores the

processed data before displaying it as output.

11

3) Processing: It is the process of converting the raw data into useful information. This

process is performed by the CPU of the computer. It takes the raw data from storage,

processes it and then sends back the processed data to storage.

4) Outputting: It is the process of presenting the processed data through output devices like

monitor, printer and speakers.

5) Controlling: This operation is performed by the control unit that is part of CPU. The

control unit ensures that all basic operations are executed in a right manner and se\

INPUT DEVICES

Following are some of the important input devices which are used in a computer −

Keyboard

Mouse

Joy Stick

Light pen

Track Ball

Scanner

Graphic Tablet

Microphone

Magnetic Ink Card Reader(MICR)

Optical Character Reader(OCR)

Bar Code Reader

Optical Mark Reader(OMR)

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.

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.

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

12

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

Designing (CAD) and playing computer games.

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.

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.

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.

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.

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.

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 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.

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.

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 labelling 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.

13

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.

OUTPUT DEVICES

1. Monitor

2. Printer

3. Headphones

4. Computer Speakers

5. Projector

6. GPS

7. Sound card

8. Video card

9. Braille reader

10. Speech – Generating device

11. J plotter

Monitor The monitor is the most common output device. It displays information in a pictorial

form or commonly referred to as pixels.More the number of pixels, the better is the picture

clarity and sharpness. It includes a screen, circuitry, and the box, in which the circuit is

enclosed. The user can view the processed data on the screen.There are two types of

Monitor screens. They are as follows:- 1. Cathode Ray Tube Monitor (CRT) 2. Flat Panel

Screen Monitors.

Cathode Ray Tube Monitor (CRT) - Cathode Ray Tube monitors use CRT technology

similar to television. This technology uses phosphorescent dots to generate pixels that form

displayed images. CRT monitor screens are large and consume more power.Flat Panel

Screen Monitors - These monitors use a thin panel design instead of CRT technology.

Printer

A printer is a hardware device that produces a hard copy version of the processed data

from the computer.It is a device that accepts texts and graphic output from the computer and

transmits the image data to the printer, usually on a paper.Printers are the most common

output device to print text or photos. Some printers can print only in black and white, but

today, almost all the printers can print monochrome and color prints.The modern-day printers

used in homes have high DPI (dots per inch), which generates high-quality images.The

printers are classified into two main types – 1. Impact printers 2. Non Impact printers.

Impact printer - This type of printer prints characters by striking on the ribbon, and

then they are pressed on the paper. This type of printer is nowadays not in use as they make

too much noise.

14

Non-Impact printer - These types of printers are those printers that print without striking on

the ribbon. The examples of non-impact printers are laser printer and inkjet printer.

Headphones

The headphones or called as earphones are hardware output devices that are either

plugged in the computer or can be wireless.We can listen to audio or watch the video

privately without disturbing others. Headphones come in various shapes and sizes.

Computer Speakers The computer speakers are the most common output devices used with a computer.

The speakers receive audio as an input from the computer or a sound card then this input may

be either in analog or digital form.External speakers are connected to a computer only if a

user requires louder sounds, more bass, or surround sound.

Projector

A projector is an output device that can take images produced by a computer and

project them onto a screen or surface.The projectors used nowadays are known as video

projectors. The projectors can produce still images or moving images.Projectors are used in

classrooms, offices, auditoriums, and also at places of worship, as it enables a group of

people to watch videos, presentations, or pictures generated from a single computer.

GPS (Global Positioning System)

Global Positioning System or GPS is a network of satellites to know the exact

location of an object on earth. The GPS is composed of a sender and a receiver computer.The

GPS comprises 24 satellites, expanded in space about 12000 miles above the earth’s surface.

Video Card

A video card is also an expansion card that is attached to the motherboard. It

processes the images and video and enhances their display quality.Most computers have basic

video and graphics capabilities, but a video card is required for getting faster and more

detailed graphics.

Braille Reader A Braille Reader is an electronic device that allows a blind person to read the text

displayed on the monitor screen.The computer sends a text to the Braille Reader, where it

translated into Braille format and displayed by raising rounded pins through a flat surface.

J plotter J plotter or simply plotter is a kind of hardware output device similar to a printer used

to draw vector graphics. Plotter generates a digitally represented hardcopy of the design.

TYPES OF COMPUTER MEMORY: PRIMARY AND SECONDARY

Although many types of memory in a computer exist, the most basic distinction is

between primary memory, often called system memory, and secondary memory, which is

more commonly called storage.

The key difference between primary and secondary memory is speed of access.

Primary memory includes ROM and RAM, and is located close to the CPU on the

computer motherboard, enabling the CPU to read data from primary memory very

quickly indeed. It is used to store data that the CPU needs imminently so that it does

not have to wait for it to be delivered.

Secondary memory by contrast, is usually physically located within a separate

storage device, such as a hard disk drive or solid state drive (SSD), which is

connected to the computer system either directly or over a network. The cost per

15

gigabyte of secondary memory is much lower, but the read and write speeds are

significantly slower.

Primary Memory Types: RAM and ROM

1. RAM, or random access memory

2. ROM, or read-only memory

1) RAM Computer Memory

The acronym RAM stems from the fact that data stored in random access memory can

be accessed – as the name suggests – in any random order. Or, put another way, any random

bit of data can be accessed just as quickly as any other bit.The most important things to

understand about RAM are that RAM memory is very fast, it can be written to as well as

read, it is volatile (so all data stored in RAM memory is lost when it loses power) and,

finally, it is very expensive compared to all types of secondary memory in terms of cost per

gigabyte. It is because of the relative high cost of RAM compared to secondary memory

types that most computer systems use both primary and secondary memory.

Types of RAM

DRAM: DRAM stands for Dynamic RAM, and it is the most common type of RAM

used in computers. The oldest type is known as single data rate (SDR) DRAM, but

newer computers use faster dual data rate (DDR) DRAM.

SRAM: SRAM stands for Static RAM, and it is a particular type of RAM which is

faster than DRAM, but more expensive and bulker, having six transistors in each cell.

The key differences between DRAM and SRAM is that SRAM is faster than DRAM -

perhaps two to three times faster - but more expensive and bulkier. SRAM is usually

available in megabytes, while DRAM is purchased in gigabytes.

2) ROM Computer Memory

ROM stands for read-only memory, and the name stems from the fact that while data

can be read from this type of computer memory, data cannot normally be written to it. It is a

very fast type of computer memory which is usually installed close to the CPU on the

motherboard.ROM is a type of non-volatile memory, which means that the data stored in

ROM persists in the memory even when it receives no power – for example when the

computer is turned off. In that sense it is similar to secondary memory, which is used for long

term storage.

Types of ROM

16

PROM PROM stands for Programmable Read-Only Memory, and it is different from

true ROM in that while a ROM is programmed (i.e. has data written to it) during the

manufacturing process, a PROM is manufactured in an empty state and then

programmed later using a PROM programmer or burner.

EPROM EPROM stands for Erasable Programmable Read-Only Memory, and as the

name suggests, data stored in an EPROM can be erased and the EPROM

reprogrammed. Erasing an EPROM involves removing it from the computer and

exposing it to ultraviolet light before re-burning it.

EEPROM EEPROM stands for Electrically Erasable Programmable Read-Only

Memory, and the distinction between EPROM and EEPROM is that the latter can be

erased and written to by the computer system it is installed in. In that sense EEPROM

is not strictly read-only.

Secondary Memory Types

Secondary memory comprises many different storage media which can be directly

attached to a computer system. These include:

hard disk drives

solid state drives (SSDs)

Optical (CD or DVD) drives

Tape drives

Differences between RAM and ROM

ROM:

Non-volatile

Fast to read

Usually used in small quantities

Cannot be written to quickly

Used to store boot instructions or firmware

Relatively expensive per megabyte stored compared to RAM

RAM:

Volatile

Fast to read and write

Used as system memory to store data (including program code) that the CPU needs to

process imminently

Relatively cheap per megabyte stored compared to ROM, but relatively expensive

compared to secondary memory

DIFFERENT TYPES OF SOFTWARE

What is a Software?

A software or computer software essentially a type of programs which enable the

users to perform some particular specific task or actually used to operate their computer. It

essentially directs all of the peripheral devices on the entire computer system- what exactly to

do and how exactly to perform a task. A software plays a key role of a mediator between the

17

user and the computer hardware. In the absence of software, a user essentially can’t perform

any task on a computer. A software product development company is the one which develops

software for the users.Typically, there are two major classifications of software, namely

System Software and Application Software.

1. System Software

A system software aids the user and the hardware to function and interact with each

other. Basically, it is a software to manage computer hardware behavior so as to

provide basic functionalities that are required by the user. In simple words, we can say

that system software is an intermediator or a middle layer between the user and the

hardware. These computer software sanction a platform or environment for the other

software to work in. This is the reason why system software is very important in

managing the entire computer system. When you first turn on the computer, it is the

system software that gets initialized and gets loaded in the memory of the system. The

system software runs in the background and is not used by the end-users. This is the

reason why system software is also known as ‘low-level software’.

Some common system software examples are:

Operating System: It is the most prominent example of System Software. It is a

collection of software that handles resources and provides general services for

the other applications that run over them. Although each Operating System is

different, most of them provide a Graphical User Interface through which a user

can manage the files and folders and perform other tasks. Every device, whether

a desktop, laptop or mobile phone requires an operating system to provide the

basic functionality to it. Some examples of Operating syst ems is Android,

CentOS, Ios, Linux, Mac OS, MS Windows.

Programming Language Translators: These are mediator programs on which

software programs rely to translate high-level language code to simpler

machine-level code. Examples of Programming Language Translators are

Interpreter, Compiler and Assemblers.

Utility: Utility software is designed to aid in analyzing, optimizing, configuring

and maintaining a computer system. It supports the computer infrastructure.

This software focuses on how an OS functions and then accordingly it decides

its trajectory to smoothen the functioning of the system.

2. Application Software

Application Software, also known as end-user programs or productivity programs are

software that helps the user in completing tasks such as doing online research, jotting

down notes, setting an alarm, designing graphics, keeping an account log, doing

calculations or even playing games. They lie above the system software. For example,

a browser is an application designed specifically for browsing the internet or MS

Powerpoint is an application used specifically for making presentations. There are

various types of application software:

Word Processors: These applications for documentation. Along with that it also

helps I storing, formatting and printing of these documents. Database

18

Software: This software is used to create and manage a database. It is also

known as the Database Management System or DBMS.

Multimedia Software: It is the software that is able to play, create or record

images, audio or video files. They are used for video editing, animation,

graphics, and image editing.

Education and Reference Software: These types of software are specifically

designed to facilitate learning on a particular subject.

Graphics Software: As the name suggests, Graphics Software has been devised

to work with graphics as it helps the user to edit or make changes in visual data

or images. It comprises of picture editors and illustration software.

UNIT-II

Computer Number System

What are the number systems in Computer?

Number systems are the technique to represent numbers in the computer system

architecture, every value that you are saving or getting into/from computer memory has a

defined number system.

Computer architecture supports following number systems.

Binary number system

Octal number system

Decimal number system

Hexadecimal (hex) number system

1) Binary Number System - A Binary number system has only two digits that are 0

and 1. Every number (value) represents with 0 and 1 in this number system. The base

of binary number system is 2, because it has only two digits.

2) Octal number system - Octal number system has only eight (8) digits from 0 to 7.

Every number (value) represents with 0,1,2,3,4,5,6 and 7 in this number system. The

base of octal number system is 8, because it has only 8 digits.

3) Decimal number system - Decimal number system has only ten (10) digits from 0

to 9. Every number (value) represents with 0,1,2,3,4,5,6, 7,8 and 9 in this number

system. The base of decimal number system is 10, because it has only 10 digits.

4) Hexadecimal number system - A Hexadecimal number system has sixteen (16)

alphanumeric values from 0 to 9 and A to F. Every number (value) represents with

0,1,2,3,4,5,6, 7,8,9,A,B,C,D,E and F in this number system. The base of hexadecimal

number system is 16, because it has 16 alphanumeric values. Here A is 10, B is 11, C

is 12, D is 13, E is 14 and F is 15.

Number system Base Used digits Example C Language

19

assignment

Binary 2 0,1 (11110000)2 int val=0b11110000;

Octal 8 0,1,2,3,4,5,6,7 (360)8 int val=0360;

Decimal 10 0,1,2,3,4,5,6,7,8,9 (240)10 int val=240;

Hexadecimal 16 0,1,2,3,4,5,6,7,8,9,

A,B,C,D,E,F

(F0)16 int val=0xF0;

Decimal Number System to Other Base

To convert Number system from Decimal Number System to Any Other Base is quite easy;

you have to follow just two steps:

A) Divide the Number (Decimal Number) by the base of target base system (in which you

want to convert the number: Binary (2), octal (8) and Hexadecimal (16)).

B) Write the remainder from step 1 as a Least Signification Bit (LSB) to Step last as a Most

Significant Bit (MSB).

Decimal to Binary Conversion Result

Decimal Number is : (12345)10

Binary Number is

(11000000111001)2

20

Decimal to Octal Conversion Result

Decimal Number is : (12345)10

Octal Number is

(30071)8

Decimal to Hexadecimal Conversion Result

Example 1

Decimal Number is : (12345)10

Hexadecimal Number is

(3039)16

Example 2 Decimal Number is : (725)10

Hexadecimal Number is

(2D5)16

Convert

10, 11, 12, 13, 14, 15

to its equivalent...

A, B, C, D, E, F

PRACTICE PROBLEMS BASED ON CONVERSION OF BASES - Problem-01:

Convert (1056)16 to ( ? )8

Solution-

Step-01: Conversion To Base 10-

(1056)16 → ( ? )10

Using Expansion method, we have- (1056)16

= 1 x 163 + 0 x 162 + 5 x 161 + 6 x 160

= 4096 + 0 + 80 + 6 = (4182)10

From here, (1056)16 = (4182)10

Step-02: Conversion To Base 8-

(4182)10 → ( ? )8

Using Division method, we have-

21

From here, (4182)10 = (10126)8 : Thus, (1056)16 = (10126)8

Problem-02:

Convert (11672)8 to ( ? )16

Solution- Step-01: Conversion To Base 10-

(11672)8 → ( ? )10

Using Expansion method, we have-

(11672)8 = 1 x 84 + 1 x 83 + 6 x 82 + 7 x 81 + 2 x 80

= 4096 + 512 + 384 + 56 + 2

= (5050)10 From here, (11672)8 = (5050)10

Step-02: Conversion To Base 16-

(5050)10 → ( ? )16

Using Division method, we have-

From here, (5050)10 = (13BA)16 : Thus, (11672)8 = (13BA)16

Problem-03:

Convert (2724)8 to ( ? )5 Solution-

Step-01: Conversion To Base 10-

(2724)8 → ( ? )10

Using Expansion method, we have-(2724)8 = 2 x 83 + 7 x 82 + 2 x 81 + 4 x 80

= 1024 + 448 + 16 + 4

= (1492)10 From here, (2724)8 = (1492)10

Step-02: Conversion To Base 5-

(1492)10 → ( ? )5

Using Division method, we have-

22

From here, (1492)10 = (21432)5

Thus, (2724)8 = (21432)5

Problem-04: Convert (3211)4 to ( ? )5

Solution-

Step-01: Conversion To Base 10- (3211)4 → ( ? )10

Using Expansion method, we have-(3211)4

= 3 x 43 + 2 x 42 + 1 x 41 + 1 x 40 = 192 + 32 + 4 + 1

= (229)10

From here, (3211)4 = (229)10

Step-02: Conversion To Base 5- (229)10 → ( ? )5

Using Division method, we have-

From here, (229)10 = (1404)5 :Thus, (3211)4 = (1404)5

Problem-05:

Convert (1001001100)2 to ( ? )6

Solution- Step-01: Conversion To Base 10-

(1001001100)2 → ( ? )10

Using Expansion method, we have-(1001001100)2

= 1 x 29 + 0 x 28 + 0 x 27 + 1 x 26 + 0 x 25 + 0 x 24 + 1 x 23 + 1 x 22 + 0 x 21 + 0 x 20 = 512 + 64 + 8 + 4

= (588)10

From here, (1001001100)2 = (588)10

Step-02: Conversion To Base 6-

(588)10 → ( ? )6 Using Division method, we have-

23

From here, (588)10 = (2420)6 Thus, (1001001100)2 = (2420)6

PRACTICE PROBLEMS BASED ON DECIMAL TO HEXADECIMAL CONVERSION-

Problems-

Convert the following numbers from base 10 to base 16-

1. (2020)10

2. (2020.65625)10

3. (172)10

Solution-

1. (2020)10

(2020)10 → (?)16

Using division method, we have-

From here, (2020)10 = (7E4)16

2. (2020.65625)10

(2020.65625)10 → ( ? )8

Here, we treat the real part and fractional part separately-

For Real Part- The real part is (2020)10

We convert the real part from base 10 to base 16 using division method same as above.

So, (2020)10 = (7E4)16

For Fractional Part-

The fractional part is (0.65625)10

We convert the fractional part from base 10 to base 16 using multiplication method. The fractional

part terminates to 0 after 2 iterations. Traverse the real part column from top to bottom to obtain the required number in base 16.

From here, (0.65625)10 = (0.A8)8

Combining the result of real and fractional parts, we have-(2020.65625)10 = (7E4.A8)16

3. (172)10

(172)10 → ( ? )16 Using division method, we have-

24

From here, (172)10 = (AC)16

PRACTICE PROBLEMS BASED ON DECIMAL TO OCTAL CONVERSION-

Problems-

Convert the following numbers from base 10 to base 8-

1. (1032)10

2. (1032.6875)10

3. (172)10

Solution-

1. (1032)10

(1032)10 → (?)8

Using division method, we have-

From here, (1032)10 = (2010)8

2. (1032.6875)10

(1032.6875)10 → ( ? )8

Here, we treat the real part and fractional part separately-

For Real Part- The real part is (1032)10

We convert the real part from base 10 to base 8 using division method same as above.

So, (1032)10 = (2010)8

For Fractional Part-

The fractional part is (0.6875)10

We convert the fractional part from base 10 to base 8 using multiplication method.The fractional part terminates to 0 after 2 iterations.

Traverse the real part column from top to bottom to obtain the required number in base 8.

From here, (0.6875)10 = (0.54)8

Combining the result of real and fractional parts, we have-(1032.6875)10 = (2010.54)8

3. (172)10

(172)10 → ( ? )8

Using division method, we have-

25

From here, (172)10 = (254)8

PRACTICE PROBLEMS BASED ON DECIMAL TO BINARY CONVERSION-

Problems-

Convert the following numbers from base 10 to base 2-

1. (18)10

2. (18.625)10

Solution-

1. (18)10

(18)10 → ( ? )2

Using division method, we have- From here, (18)10 = (10010)2

2. (18.625)10

(18.625)10 → ( ? )2

Here, we treat the real part and fractional part separately-

For Real Part- The real part is (18)10

We convert the real part from base 10 to base 2 using division method same as above. So, (18)10 = (10010)2

For Fractional Part- The fractional part is (0.625)10

We convert the fractional part from base 10 to base 2 using multiplication method. Using multiplication method, we have-

Explanation

Step-01:

Multiply 0.625 with 2. Result = 1.25.

Write 1 in real part and 0.25 in fractional part. Step-02:

Multiply 0.25 with 2. Result = 0.50.

Write 0 in real part and 0.50 in fractional part. Step-03:

Multiply 0.50 with 2. Result = 1.0.

Write 1 in real part and 0.0 in fractional part. Since fractional part becomes 0, so we stop.

The fractional part terminates to 0 after 3 iterations. Traverse the real part column from top to bottom to obtain the required number in base 2.

From here, (0.625)10 = (0.101)2

Combining the results of real part and fractional part, we have-(18.625)10 = (10010.101)2

26

PRACTICE PROBLEMS BASED ON CONVERSION TO BASE 10-

Convert the following numbers to base 10-

1. (10010)2

2. (254)8

3. (AC)16

Solutions-

1. (10010)2

(10010)2 → ( ? )10 Using expansion method, we have-(10010)2

= ( 1 x 24 + 0 x 23 + 0 x 22 + 1 x 21 + 0 x 20 )10 = ( 16 + 0 + 0 + 2 + 0 )10

= ( 18 )10

2. (254)8

(254)8 → ( ? )10 Using expansion method, we have-(254)8

= ( 2 x 82 + 5 x 81 + 4 x 80 )10

= ( 128 + 40 + 4 )10 = ( 172 )10

3. (AC)16

(AC)16 → ( ? )10 Using expansion method, we have-(AC)16 = ( A x 161 + C x 160 )10

= ( 10 x 16 + 12 x 1 )10

= ( 160 + 12 )10

= ( 172 )10

27

UNIT-III

FLOW CHART

A flowchart is a diagram that depicts a process, system or computer algorithm. They

are widely used in multiple fields to document, study, plan, improve and communicate often

complex processes in clear, easy-to-understand diagrams. Flowcharts, sometimes spelled as

flow charts, use rectangles, ovals, diamonds and potentially numerous other shapes to define

the type of step, along with connecting arrows to define flow and sequence. They can range

from simple, hand-drawn charts to comprehensive computer-drawn diagrams depicting

multiple steps and routes.

The following steps are involved in using a computer as a problem-solving tool:

1. Develop an algorithm and a flowchart.

2. Write the program in a computer language (such as Fortran or C).

3. Enter the program into the computer.

4. Test and debug the program.

5. Run the program, input data and get the results from the computer.

28

COMMONLY USED SYMBOLS IN DETAILED FLOWCHARTS

rectangle - flowchart process stepOne step in the process. The step is written inside the box.

Usually, only one arrow goes out of the box.

Direction of flow from one step or decision to another.

Decision based on a question. The question is written in the diamond. More than one

arrow goes out of the diamond, each one showing the direction the process takes for a given answer to

the question. (Often the answers are "yes" and "no.")

Delay or wait

Link to another page or another flowchart. The same symbol on the other page indicates that

the flow continues there.

Input or output

Document

Alternate symbols for start and end points

DATA PROCESSING SYSTEM

A data processing system is a combination of machines, people, and processes that for a set

of inputs produces a defined set of outputs. The inputs and outputs are interpreted

as data, facts, information etc. depending on the interpreter's relation to the system.

A term commonly used synonymously with data or storage (codes) processing

system is information system.With regard particularly to electronic data processing, the

corresponding concept is referred to as electronic data processing system.

A data processing system may involve some combination of:

Conversion converting data to another form or Language.

Validation – Ensuring that supplied data is "clean, correct and useful."

29

Sorting – "arranging items in some sequence and/or in different sets."

Summarization – reducing detail data to its main points.

Aggregation – combining multiple pieces of data.

Analysis – the "collection, organization, analysis, interpretation and presentation of

data.".

Reporting – list detail or summary data or computed information.

What is Network?

In the today world, Two devices are in network if a process in one device is able to

exchange information with a process in another device. Networks are known as a medium of

connections between nodes (set of devices) or computers. A network is consist of group

of computer systems, servers, networking devices are linked together to share resources,

including a printer or a file server. The connections is established by using either cable

media or wireless media.

Types of Networks

LAN

A Local Area Network is a privately owned computer network covering a small Networks

geographical area, like a home, office, or groups of buildings e.g. a school Network. A LAN

is used to connect the computers and other network devices so that the devices can

communicate with each other to share the resources. The resources to be shared can be a

hardware device like printer, software like an application program or data. The size of LAN

is usually small. The various devices in LAN are connected to central devices called Hub or

Switch using a cable. There are basically two types of Local Area Networks

namely: ARCnet and Ethernet.

MAN

MAN stands for Metropolitan Area Networks is one of a number of types of networks. A

MAN is a relatively new class of network. MAN is larger than a local area network and as its

name implies, covers the area of a single city. MANs rarely extend beyond 100 KM and

frequently comprise a combination of different hardware and transmission media. It can be

single network such as a cable TV network, or it is a means of connecting a number of LANs

into a larger network so that resources can be shared LAN to LAN as well as device to

device.

WAN

A wide area network (WAN) is a telecommunication network. A wide area network is simply

a LAN of LANs or Network of Networks. WANs connect LANs that may be on opposite

sides of a building, across the country or around the world. WANS are characterized by the

slowest data communication rates and the largest distances. WANs can be of two types: an

enterprise WAN and Global WAN.

30

WLANs

WLANs (Wireless Local Area Networks or sometimes referred to as LAWN, for local area

wireless network) provide wireless network communication over short distances using radio

or infrared signals instead of traditional network cabling.WLANs (Wireless Local Area

Networks) is one in which a mobile user can connect to a local area network (LAN) through a

wireless (radio) connection. Norman Abramson, a professor at the University of Hawaii,

developed the world’s first wireless computer communication network,

A WLAN typically extends an existing wired local area network. WLANs (Wireless

Local Area Networks) are built by attaching a device called the access point (AP) to the

edge of the wired network. Clients communicate with the AP using a wireless network

adapter similar in function to a traditional Ethernet adapter. Network security remains an

important issue for WLANs (Wireless Local Area Networks). Random wireless clients must

usually be prohibited from joining the WLAN. Technologies like WEP raise the level of

security on wireless networks to rival that of traditional wired networks.

UNIT - IV

OPERATING SYSTEM

An Operating system (OS) is a software which acts as an interface between the end

user and computer hardware. Every computer must have at least one OS to run other

programs. An application like Chrome, MS Word, Games, etc needs some environment in

which it will run and perform its task. The OS helps you to communicate with the computer

without knowing how to speak the computer's language. It is not possible for the user to use

any computer or mobile device without having an operating system.

Features of Operating System

Protected and supervisor mode

Allows disk access and file systems Device drivers Networking Security

Program Execution

Memory management Virtual Memory Multitasking

Handling I/O operations

Manipulation of the file system

Error Detection and handling

Resource allocation

Information and Resource Protection

Functions of an Operating System

1. Process management:- Process management helps OS to create and delete processes.

It also provides mechanisms for synchronization and communication among

processes.

31

2. Memory management:- Memory management module performs the task of

allocation and de-allocation of memory space to programs in need of this resources.

3. File management:- It manages all the file-related activities such as organization

storage, retrieval, naming, sharing, and protection of files.

4. Device Management: Device management keeps tracks of all devices. This module

also responsible for this task is known as the I/O controller. It also performs the task

of allocation and de-allocation of the devices.

5. I/O System Management: One of the main objects of any OS is to hide the

peculiarities of that hardware devices from the user.

6. Secondary-Storage Management: Systems have several levels of storage which

includes primary storage, secondary storage, and cache storage. Instructions and data

must be stored in primary storage or cache so that a running program can reference it.

7. Security:- Security module protects the data and information of a computer system

against malware threat and authorized access.

8. Command interpretation: This module is interpreting commands given by the and

acting system resources to process that commands.

9. Networking: A distributed system is a group of processors which do not share

memory, hardware devices, or a clock. The processors communicate with one another

through the network.

10. Job accounting: Keeping track of time & resource used by various job and users.

11. Communication management: Coordination and assignment of compilers,

interpreters, and another software resource of the various users of the computer

systems.

Types of Operating system

Batch Operating System

Multitasking/Time Sharing OS

Multiprocessing OS

Real Time OS

Distributed OS

Network OS

Mobile OS

Batch Operating System

Some computer processes are very lengthy and time-consuming. To speed the same

process, a job with a similar type of needs are batched together and run as a group.

The user of a batch operating system never directly interacts with the computer. In this type

of OS, every user prepares his or her job on an offline device like a punch card and submit it

to the computer operator.

Multi-Tasking/Time-sharing Operating systems

Time-sharing operating system enables people located at a different terminal(shell) to

use a single computer system at the same time. The processor time (CPU) which is shared

among multiple users is termed as time sharing.

Real time OS

A real time operating system time interval to process and respond to inputs is very

small. Examples: Military Software Systems, Space Software Systems.

32

Distributed Operating System

Distributed systems use many processors located in different machines to provide

very fast computation to its users.

Network Operating System

Network Operating System runs on a server. It provides the capability to serve to

manage data, user, groups, security, application, and other networking functions.

Mobile OS

Mobile operating systems are those OS which is especially that are designed to power

smartphones, tablets, and wearables devices.

TYPES OF OS

Any operating system which runs from the hard disk drive is termed as Disk

Operating System ( D.O.S ). This also refers to the specific family of disk operating system

which is also known as MS-DOS or Microsoft disk operating system. Anything which

commands and controls the computer’s hardware and its peripheral devices with control over

the program and its functionality is known as the operating system. This operating system

which runs through the hard disk is known as a disk operating system. For the very first time,

It was made and introduced for IBM by Microsoft which was known as IBM PC DOS in the

year 1981.

Features of DOS

It is a 16-bit operating system

The maximum space available is 2 GB.

It is a free OS.

It uses a text-based interface and requires text and codes to operate

It does not support graphical interface

It is a single user operating system.

Advantages

We have direct access to the BIOS and its underlying hardware.

Due to its size, it will “boot” much faster than any windows version, thus it will run in

a smaller system.

It is very lightweight so it does not have the overhead of the multitasking operating

system.

It is good for making workarounds for managing/administering an MS system, and for

combining programs.

Disadvantages

No multi-tasking supported by the OS.

Difficulty in memory access when addressing more than 640 MB of RAM.

Interrupt levels for hardware needs to be managed by our self.

Automatic IRQ ordering is not supported by the OS.

UNIX

UNIX is an operating system which was first developed in the 1960s, and has been under

constant development ever since. By operating system, we mean the suite of programs

which make the computer work. It is a stable, multi-user, multi-tasking system for servers,

desktops and laptops.

Advantages

33

o Full multitasking with protected memory. Multiple users can run multiple programs

each at the same time without interfering with each other or crashing the system.

o Very efficient virtual memory, so many programs can run with a modest amount of

physical memory.

o Access controls and security. All users must be authenticated by a valid account and

password to use the system at all. All files are owned by particular accounts. The

owner can decide whether others have read or write access to his files.

o A powerfully unified file system. Everything is a file: data, programs, and all physical

devices. Entire file system appears as a single large tree of nested directories,

regardless of how many different physical devices (disks) are included.

Disadvantages

o The traditional command line shell interface is user hostile -- designed for the

programmer, not the casual user.

o Commands often have cryptic names and give very little response to tell the user what

they are doing. Much use of special keyboard characters - little typos have unexpected

results.

o To use Unix well, you need to understand some of the main design features. Its power

comes from knowing how to make commands and programs interact with each other,

not just from treating each as a fixed black box.

o Richness of utilities (over 400 standard ones) often overwhelms novices.

Documentation is short on examples and tutorials to help you figure out how

to use the many tools provided to accomplish various kinds of tasks.

LINUX

Linux is an open source operating system (OS). An operating system is the software that

directly manages a system's hardware and resources, like CPU, memory, and storage.

The OS sits between applications and hardware and makes the connections between all of

your software and the physical resources that do the work.

Advantages of Linux operating system

Open source:-

Linux is an open-source OS that means anyone can see the source code and change it

according to his needs. You can freely install Linux on many computers without getting

paid license. If we compare this with windows or mac then they are paid operating

systems. You have to get license of windows and mac to use on your machine.

No anti-virus software needed:-

In Linux, you do not need anti-virus software to be installed on your PC. Linux has fewer

chances to be affected with virus. The reason for strong virus protection is that Linux has

large number of open source developers which keeps an eye on virus-related stuff. If any

source code needs to be updated then it is done in no time.

Text editors:-

Linux has a vast range of text editors available. If you are a programmer then you can

pick any of free software packages like visual studio code, Vim, Atom etc. Most of text

editors are freely available and you can use it without any issue.

Powerful command prompt:-

34

Command prompt in Linux is very advanced and if you are developer then you can

perform most of your work using the command-line interface. You can install different

repositories and packages through the command-line interface.

No reboot needed:-

If you are windows user then you have seen system reboot while you install/uninstall any

software or rebooting when the system becomes slow. But in case of Linux, you do not

need to reboot your system in such cases.

Low system specifications:-

If you have an old computer that has low specification then you can still run Linux. Linux

has different distributions that are available for all types of computers e.g. large scale

computers, servers, Pc etc.

Good at multitasking:-

If you want to do some batch works like printing a large file or downloading large file

then you can concurrently perform other tasks like typing or coding any program. Linux

is good in doing such multitasking and your system will not slow down.

Less disk space needed:-

If you have limited disk space then you can still run Linux. You do not need extra disk

space for running Linux for a longer time.

File formats:-

Linux supports a large number of file formats. So you have to not worry if any file format

does not run on Linux. You can install different software packages for specific file format

and it will work fine.

Disadvantages of Linux operating system

Hardware drivers:-

One of the issues that most Linux users face is that some hardware drivers are not

available for Linux. Hardware companies prefer to make drivers for windows or mac

because they have more users as compared to Linux.

Learning curve:-

Getting started with windows is easy for beginners but learning Linux is difficult. You

have to learn about the command-line interface and searching for new software is also

little bit difficult. If you face any problem in the operating system then finding solution is

problematic. There are fewer experts for Linux as compared to windows and mac.

Software alternative:-

Take an example of Photoshop which is a popular graphic editing tool. Photoshop is

available for windows but is not present in Linux. There are other photo editing tools but

Photoshop is a more powerful tool than others. MS office is another example which is not

available for Linux users.

Games:-

Most of the games are made for windows but not Linux. As windows platform is widely

used so game developers have more interest in windows.

WINDOWS

Microsoft Windows, also called Windows and Windows OS, computer operating

system (OS) developed by Microsoft Corporation to run personal computers (PCs).

Featuring the first graphical user interface (GUI) for IBM-compatible PCs, the Windows

OS soon dominated the PC market.

35

WINDOWS XP

Windows XP is expensive to buy, It cannot be installed onto multiple computers

because it only has a single user license, It is prone to crashing, therefore, making it

unstable, and it cannot be run on old hardware.

WINDOWS NT

Windows NT (New Technology) is a 32-bit operating system that supports

preemptive multitasking. There are actually two versions of Windows NT: Windows

NT Server, designed to act as a server in networks, and Windows NT Workstation for stand-

alone or client workstations.

Advantages of windows operating system

Support for all hardware: As windows OS is used by 95% of users so most of the

hardware vendors make drivers for windows.

Ease of use: All versions of Microsoft Windows have something common in it which

makes users easy to shift from one version to another. Windows 7 users have no difficulty

in migrating to Windows 10 because most of the features of Windows 10 are the same as

windows 7. The user interface of windows is also easy to use than UNIX and MAC.

Software support: Windows platform is best suited for game and software developers.

Windows have large number audience so developers prefer to make utilities, games and

software for windows OS. Linux users cannot make windows apps so it is better to use

windows for developing apps.

Plug and play feature: Most hardware can be detected automatically by plug and play

feature. You do not need to manually install the hardware but it is ready to use when

attached e.g. webcam, keyboard, mouse, mobile device etc.

Desktop and touch screen: Windows 10 is made for both touch screen devices and

desktop computers. The user interface of Windows 10 is made in such a way that it works

better for any type of windows device.

Disadvantages of Windows operating system

Virus attacks: Windows have a high amount of hacker attacks. The hackers can easily

break windows security. So windows users are dependent on anti-virus software and have

to pay monthly charges to companies to protect their data. Also, windows users have to

update OS to keep up-to-date with security patches.

Most of the software is paid: Most windows programs are paid e.g. games, graphics

software (Photoshop), download manager (IDM) and other popular software are paid.

You have to buy these software or pay a monthly fee to use them.

Rebooting a system: If your system becomes slow in performance then you have to

reboot it. If you load many programs at the same time then your system slows down and

hangs up. The only solution for this is to reboot.

High price: Linux OS is open source and is free to use for everyone but windows OS has

paid license and you cannot use windows OS legally free. The cost of buying a copy of

windows OS is high as well. You also need to buy other Microsoft software e.g. MS

Office to do regular office work on the computer.

High computer resources: If you are installing windows OS then your computer should

have high ram capacity, a lot of hard drive space and good graphics card. This is because

of features that are used in windows. If you want to install graphics software i.e.

Photoshop then 16 GB of ram is recommended.

36

Technical support: Windows support is not good for most users. Only some large

organizations can get good support from the windows team. Common users have to

search for forums to get their problem solved.

37

UNIT – V

INTERNET

The internet is the wider network that allows computer networks around the world run

by companies, governments, universities and other organisations to talk to one another. The

result is a mass of cables, computers, data centres, routers, servers, repeaters, satellites and

wifi towers that allows digital information to travel around the world.It is that infrastructure

that lets you order the weekly shop, share your life on Facebook, stream Outcast on Netflix,

email your aunt in Wollongong and search the web for the world’s tiniest cat.

WWW

The web is a way to view and share information over the internet. That information,

be it text, music, photos or videos or whatever, is written on web pages served up by a web

browser.Google handles more than 40,000 searches per second, and has 60% of the global

browser market through Chrome. There are nearly 2bn websites in existence but most are

hardly visited. The top 0.1% of websites (roughly 5m) attract more than half of the world’s

web traffic.

Among them are Google, YouTube, Facebook, the Chinese site Baidu, Instagram,

Yahoo, Twitter, the Russian social network VK.com, Wikipedia, Amazon and a smattering of

porn sites. The rise of apps means that for many people, being on the internet today is less

about browsing the open web than getting more focused information: news, messages,

weather forecasts, videos and the like.

Differences between WWW and Internet

WWW (World Wide Web) Internet

The World Wide Web is the common system for

navigating the internet. It is not the only system that can be used for such access, but it is by far the most

common one.

The internet is a public network of network with a

maze of wired and wireless connections between separate groups of servers computers and countless

devices from around the world

The World Wide Web is distinguished from other

systems through its use of HTTP (Hypertext Transfer

Protocol). It can be safely said that the HTTP is the

language of the World Wide Web

Along with Internters, there also exist the Intranets,

which is the same type of information network but

more privatized in order to control access.

WWW is more software-oriented as compared to the

Internet

Internet is primarily hardware-based.

The HTTP along with being the language of the World Wide Web also governs it by dealing with linking of

files, documents and other resources

The internet is governed by a set of rules and regulations collectively known as Internet Protocol

(IP). The IP deals with data transmitted through the

internet.

38

EVLOUTION OF THE INTERNET

Phase one: from military experiment to civilian utility (1967–1995)

As with most technologies (Arthur 2011), the roots of the Internet go back a long

way, mostly to the post-World War II era, but in some respects to the late 1930s.5 The

evolution of the network to date can be summarised in terms of two main phases: its

development from a military experiment to a civilian utility, and the commercialisation of the

network.

Pre-history: 1956–1966

That the Internet owes its existence to the Cold War is well known. But, as ever,

retrospective generalisation glosses over a more complicated story.

The first strand of this concerns the doctrine of ‘mutual assured destruction’ (MAD) which

governed the nuclear stand-off between the United States and the Soviet Union. MAD

supposedly ensured national security by guaranteeing that if one side launched a nuclear

attack, the other would retaliate in (devastating) kind. There was, however, one apparent flaw

in the logic, in that the doctrine could give an advantage to the aggressor if his pre-emptive

strike was so devastating that it rendered the enemy's command-and-control system

inoperative, thereby making it impossible to retaliate.

The ARPANET: 1967–1972

The idea of a ‘resource-sharing’ network first emerged in ARPA in 1966

(Naughton 1999, 84). Design work, conducted in a collegial style (Abbate 1999, 56) unusual

in the defence industry, then proceeded over the next two years. The contract to build the

network was awarded in early 1969 to Bolt, Beranek and Newman, a Boston-based

consultancy firm with strong links to MIT.

The technological and conceptual challenges that faced the network's designers have

long been obliterated by the omniscience of hindsight, but they were formidable.7 Given that

the network was supposed to facilitate the sharing of expensive and scarce resources, namely

the mainframe computers that ARPA had funded in various research centres across the

country, a key obstacle to overcome was the fact that these machines were incompatible with

one another. For each of them to participate in a network would require the creation of

complex, customised networking software which would enable each machine to

communicate with every other machine on the system. In the end, this problem was not so

much solved as side-stepped: it was decided to build a ‘sub-net’ of identical minicomputers

(which came to be called ‘interface message processors’ or IMPs) each linked to a single

mainframe ‘host’. In that way the task of writing networking software for a host was greatly

39

reduced: it would simply have to communicate with a single machine – the IMP assigned to

it.

Development of the TCP/IP-based ‘internetwork’: 1973–1983

During and after the construction of the ARPANET, other significant developments in

networking technology were under way. At the University of Hawaii, researchers had built

ALOHA – a packet-switched network that operated, not over leased telephone lines, as

ARPANET did, but via radio. Within ARPA, it was decided to build on this work by creating

a packet-switched radio network (named PRNET) in the San Francisco area. The motivation

for this was obvious: ARPA was part of the US Department of Defense and its planners were

interested in the potential of packet switching for command-and-control in battlefield

conditions. The agency had also begun to experiment with using the technology in satellite

communications, for example, for linking seismic monitoring stations in Scandinavia

(established to monitor Soviet nuclear testing) with the US, via a network which was

christened SATNET.

Transition from a military/research network to a ‘civilian’ one: 1983–1995

The creation of the MILNET domain meant that ARPANET returned to being a

research-focused network dominated by universities and research institutions, so the breach

was an essential first step towards achieving ARPA's goal of transferring the network to

civilian control. The second step was to take measures to foster the dissemination of TCP/IP

technology within the computer industry. To that end, ARPA funded various operators to

create TCP implementations for various operating systems

Phase two: the commercial Internet (1995–present)

The first Internet boom: 1995–2000

In the 1980s, ‘cyberspace’ – the term coined by the novelist William Gibson to

describe the virtual world behind the computer screen (Gibson 1984) – was an unusual space.

It was essentially a geek preserve, with a social ethos that was communal, libertarian,

collaborative, occasionally raucous, anti-establishment and rich in debate and discussion (see

Hauben and Hauben 1997). It had no commerce, no hierarchies, no crime and no spam, and

in general it was populated by people who either knew one another, or at least knew others’

institutional affiliations. In that sense, cyberspace and the so-called real world existed as

parallel universes. Most people outside of the magic circle had no knowledge of the network

– and even if they did, they would have found it difficult to gain admission to it.

40

Web 2.0’: 2000–2003

The Web was originally conceived as a means of sharing information among particle

physicists who were scattered across the world. Since most of that information was in the

form of documents, the design was therefore for a system that would make it possible to

format these documents in a standardised way, publish them online, and make them easy to

access. So the first ‘release’ of the Web (to use a software term) created a worldwide

repository of linked, static documents held on servers distributed across the Internet.

Mobile connectivity, surveillance, cybercrime, corporate power, changing patterns of

use and their implications: (2004–present)

The most recent phase in the evolution of the Internet has been characterised by

significant changes in the ways that people access and use the network and by the ways in

which the infrastructure of the network has evolved to cope with these changes.

SERVICES OF INTERNET

Internet Services allows us to access huge amount of information such as text,

graphics, sound and software over the internet. Following diagram shows the four different

categories of Internet Services.

Communication Services

There are various Communication Services available that offer exchange of information

with individuals or groups. The following table gives a brief introduction to these services:

1. Electornic mail, 2. tel net, 3. Newsgroup 4. Mailing lists 5. Internet relay chat

6. Instant messaging 8. Internet telephony

Information Retrieval Services

There exist several Information retrieval services offering easy access to information

present on the internet. The following table gives a brief introduction to these services:

1. File transfer protocol, 2. Archie 3. Gopher

Web Services

Web services allow exchange of information between applications on the web. Using

web services, applications can easily interact with each other.

World Wide Web (WWW)

It offers a way to access documents spread over the several servers over the internet.

These documents may contain texts, graphics, audio, video, hyperlinks. The hyperlinks allow

the users to navigate between the documents.

41

Video Conferencing

Video conferencing or Video teleconferencing is a method of communicating by two-

way video and audio transmission with help of telecommunication technologies.Modes of

Video Conferencing: 1. Point-to-Point - This mode of conferencing connects two locations

only. 2. Multi-point - This mode of conferencing connects more than two locations

through Multi-point Control Unit (MCU).

INTERNET PROTOCOLS

The Internet Protocol (IP) is a protocol, or set of rules, for routing and addressing

packets of data so that they can travel across networks and arrive at the correct destination.

Data traversing the Internet is divided into smaller pieces, called packets. IP information is

attached to each packet, and this information helps routers to send packets to the right place.

Every device or domain that connects to the Internet is assigned an IP address, and as packets

are directed to the IP address attached to them, data arrives where it is needed.

TYPES

1. Transmission Control Protocol (TCP): TCP is a popular communication protocol

which is used for communicating over a network. It divides any message into series of

packets that are sent from source to destination and there it gets reassembled at the

destination.

2. Internet Protocol (IP): IP is designed explicitly as addressing protocol. It is mostly

used with TCP. The IP addresses in packets help in routing them through different

nodes in a network until it reaches the destination system. TCP/IP is the most popular

protocol connecting the networks.

3. User Datagram Protocol (UDP): UDP is a substitute communication protocol to

Transmission Control Protocol implemented primarily for creating loss-tolerating and

low-latency linking between different applications.

4. Post office Protocol (POP): POP3 is designed for receiving incoming E-mails.

5. Simple mail transport Protocol (SMTP): SMTP is designed to send and distribute

outgoing E-Mail.

6. File Transfer Protocol (FTP): FTP allows users to transfer files from one machine to

another. Types of files may include program files, multimedia files, text files, and

documents, etc.

42

7. Hyper Text Transfer Protocol (HTTP): HTTP is designed for transferring a hypertext

among two or more systems. HTML tags are used for creating links. These links may

be in any form like text or images. HTTP is designed on Client-server principles

which allow a client system for establishing a connection with the server machine for

making a request. The server acknowledges the request initiated by the client and

responds accordingly.

8. Hyper Text Transfer Protocol Secure (HTTPS): HTTPS is abbreviated as Hyper Text

Transfer Protocol Secure is a standard protocol to secure the communication among

two computers one using the browser and other fetching data from web server. HTTP

is used for transferring data between the client browser (request) and the web server

(response) in the hypertext format, same in case of HTTPS except that the transferring

of data is done in an encrypted format. So it can be said that https thwart hackers from

interpretation or modification of data throughout the transfer of packets.

9. Telnet: Telnet is a set of rules designed for connecting one system with another. The

connecting process here is termed as remote login. The system which requests for

connection is the local computer, and the system which accepts the connection is the

remote computer.

10. Gopher: Gopher is a collection of rules implemented for searching, retrieving as well

as displaying documents from isolated sites. Gopher also works on the client/server

principle.

INTERNET SERVERS AND CLIENTS

A computer network in which one centralized, powerful computer (called the server)

is a hub to which many less powerful personal computers or workstations (called clients) are

connected. The clients run programs and access data that are stored on the server. Compare

peer-to-peer network.

Internet servers make the Internet possible. All of the machines on the Internet are

either servers or clients. The machines that provide services to other machines are servers.

And the machines that are used to connect to those services are clients. There are Web

servers, e-mail servers, FTP servers and so on serving the needs of Internet users all over the

world.

NETWORK STRUCTURE / TOPOLOGY

A computer network is comprised of nodes and links, a node is the end point of any

branch in a computer, a terminal device, workstation or interconnecting equipment facility. A

43

link is a communication path between two nodes. The terms “circuit” and “Channel” are

frequently used as synonyms for the link.

Network Topology is the study of the arrangement or mapping of the elements (links,

nodes, etc.) of a network interconnection between the nodes.

1. Bus Topology

This structure is very popular for local area networks. In this structure or topology, a

single network cable runs in the building or campus and all nodes are linked along with this

communication line with two endpoints called the bus or backbone as show figure. By this

type of topology, if one node goes faulty all nodes may be affected as all nodes share the

same cable for the sending and receiving of information. The cabling cost of bus systems is

the least of all the different topologies. Each end of the cable is terminated using a special

terminator.

[A].Advantages: − Reliable in very small networks as well as easy to use and

understand. − Requires least amount of cable to connect the computers (nodes) together and

therefore is less expensive than other cabling arrangements. − It's easy to extend, Two cables

can be easily joined with a connector, making a longer cable for more computers to join the

network. − A repeater can also be used to extend a bus configuration.

[B]. Disadvantages: − Heavy network traffic can slow a bus considerably because any

computer can transmit at any time. But networks do not Coordinate when information is sent.

Computer interrupting each other can use a lot of bandwidth. − Each connection between two

cables weakens the electrical signal. − The bus configuration can be difficult to find and can

cause the whole networks to stop functioning.

2. Ring Topology

This is yet another structure for local area networks. In this topology, the network

cable passes from one node to another until all nodes are connected in the form of a loop or

ring. There is a direct point-to-point link between two neighboring nodes (the Next and the

Previous). These links are unidirectional which ensures that transmission by a node traverses

the whole ring and comes back to the node.

Information travels around the ring from one node to the next. Each packet of data

sent to the rink is prefixed by the address of the station to which it is being sent. When a

packet of data arrives, the node checks to see if the packet address is the same as its own, if it

is, it grabs the data in the packet. If the packet does not belong to it, it sends the packet to the

next node in the ring. Faulty nodes can be isolated from the ring. When the workstation is

powered on, it connects itself to the ring. When power is off, it disconnects itself from the

44

ring and allows the information to bypass the node. The most common implementation of this

topology is token ring. A break in the ring causes the entire network to fail. Individual nodes

can be isolated from the ring.

[A]. Advantages: − Ring networks offer high performance for a small number of

workstations or for larger networks where each station has a similar workload. − Ring

networks can span longer distances than other types of networks. − Ring networks are easily

extendable. − Unlike Bus topology, there is no signal loss in Ring topology because the

tokens are data packets that are re-generated at each node.

[B]. Disadvantages: − Relatively expensive and difficult to install − Failure of one

computer on the network can affect the whole network. − It is difficult to find fault in a ring

network. − Adding or removing computers can disrupt the network. − It is much slower than

an Ethernet network under normal load.

3. Star Topology

Star topology uses a central hub through which, all components are connected. In a

Star topology, the central hub is the host computer, and at the end of each connection is a

terminal. Nodes communicate across the network by passing data through the hub. A star

network uses a significant amount of cable as each terminal is wired back to the central hub,

even if two terminals are side by side but several hundred meters away from the host. The

central hub makes all routing decisions, and all other workstations can be simple. An

advantage of the star topology is that failure, in one of the terminals does not affect any other

terminal; however, failure of the central hub affects all terminals. This type of topology is

frequently used to connect terminals to a large time-sharing host computer.

[A]. Advantages: − It is more reliable (if one connection fails, it does not affect

others) − The center of a star network is a good place to diagnose network faults and if one

computer fails whole network is not disturbed. Hub detects the fault and isolates the faulty

computer. − It is easy to replace, install or remove hosts or other devices, the problem can be

easily detected-It is easier to modify or add a new computer without disturbing the rest of the

network by simply running a new line from the computer to the central location and plugging

it to the hub. − Use of multiple cable types in a same network with a hub. − It has good

performance

[B]. Disadvantages − It is expensive to install as it requires more cable, it costs more

to cable a star network because all network cables must be pulled to one central point,

requiring more cable length than other networking topologies. − Central node dependency, if

45

central hub fails, the whole network fails to operate. − Many star networks require a device at

the central point to rebroadcast or switch the network traffic.

4. Mesh Topology

Devices are connected with many redundant interconnections between network nodes.

In a well-connected topology, every node has a connection to every other node in the

network. The cable requirements are high, but there are redundant paths built in. Failure in

one of the computers does not cause the network to break down, as they have alternative

paths to other computers.

[A]. Advantages − Yield the greatest amount of redundancy in the event that one of

the nodes fails where network traffic can be redirected to another node. − Point-to-point link

makes fault isolation easy. − Privacy between computers is maintained as messages travel

along dedicated path. − Network problems are easier to diagnose.

[B]. Disadvantages − The amount of cabling required is high. − A large number of I/O

(input/output) ports are required. VI. Tree Topology The most common structure or topology

known as Tree topology, Tree topology is a LAN topology in which only one route exists

between any two nodes on the network. The pattern of connection resembles a tree in which

all branches spring from one root.

5. Tree topology

It is a hybrid topology, it is similar to the star topology but the nodes are connected to

the secondary hub, which in turn is connected to the central hub. In this topology group of

star-configured networks are connected to a linear bus backbone.

[A]. Advantages − Installation and configuration of network are easy. − The addition

of the secondary hub allows more devices to be attached to the central hub. − Less expensive

when compared to mesh topology. − Faults in the network can be detected traces.

[B]. Disadvantages −Failure in the central hub brings the entire network to a halt.

−More cabling is required when compared to the bus topology because each node is

connected to the central hub.

INTRANET

"Intranet" is a private network used by an organisation. The primary purpose of

an intranet is to help employees to securely communicate among each other, to store

information and to help collaboration. Examples of intranet services include Microsoft

SharePoint, Huddle, Igloo, and Jostle. While some services are open source and free of

charge, most intranet solutions require a monthly fee. The cost is usually related to the

number of users within the intranet.

46

EXTRANET

It is often defined as a private network that leverages internet technology and public

telecommunication system to share part of a business's information or operations over a

secure system with suppliers, vendors, partners, customers, or other businesses. A

good example of an extranet network would be Share point.

INTERNET VS INTRANET VS EXTRANET IN TABULAR FORM

BASIS OF

COMPARISON INTERNET INTRANET EXTRANET

Description

Internet can be

described as a global

system of

interconnected

computer network.

Intranet can be

described as a

network of computers

or a private network

designed for a

specific group of

users (organization).

Extranet can be

described as a private

network that uses

public network to

share information with

clients (suppliers and

vendors).

Size Of The

Network

Internet is the largest

network in as far as

the number of

connected devices is

concerned.

It is a small network

with a few number of

connected devices.

It is a small network

with a few number of

connected devices.

Purpose

Internet is a means of

sharing information

throughout the world.

Intranet is a means of

sharing sensitive or

confidential

information

throughout the

organization.

Extranet is a means of

conveying information

between members of

the organization and

external members.

Regulation It is not regulated by

any authority.

It is regulated by a

specific organization.

It is regulated by

multiple

organizations.

Content On The

Network

Content in the

network is readily

accessible by

everyone who is

connected.

The content in the

network is accessible

only to members of

the organization.

The content on the

network is accessible

to members of the

organization and

external members with

access to the network.

Ownership Internet has no known

ownership.

Ownership of intranet

is by a single

organization.

Ownership of extranet

is by a single or

multiple

organizations.

Mechanism Of Internet is unregulated Intranet is regulated Extranet is also

47

Regulation and uncensored. by the organization

policies.

regulated by

contractual

agreements between

organizations.

Access

Users have

unrestricted access

and can access

internet anonymously.

An intranet may be

accessible from the

internet, but it is

protected by a

password and

accessible only to

authorized users.

An intranet may be

accessible from the

internet, but it is

protected by a

password and

accessible only to

authorized users.

Security

Security is dependent

of the user of the

device connected to

network.

Security of the

network is enforced

through a firewall.

Security of the

network is enforced

through a firewall that

separates internet and

extranet.

Example

An example of

internet is the network

you use to google

words with.

An example intranet

is a company like

ExxonMobil using

internal network for

its business

operations.

Example of extranet is

when companies like

HP, Intel and Lenovo

decide to use the same

network for related

business operations.