Computer

Index

Computer

Evolution of computer

Computer generations

Characteristics of computer

Uses of computer

Classification of computer

Computer organization

Computer

The word “computer” comes from the word “compute”, which means, “to calculate”. Hence,

people usually consider a computer to be a calculating device that can perform arithmetic

operations at high speed.

A computer is a programmable machine designed to perform arithmetic and logical operations

automatically and sequentially on the input given by the user and gives the desired output after

processing. However, more than 80% of work done by computers today is of non-mathematical or

non-numerical nature.

More accurately, we can define a computer as a device that operates upon data. Data can be

anything. It comes in various shapes and sizes depending upon the type of computer application.

A computer can store, process and retrieve data as and when required. The fact that the computer

processes data is so fundamental that many people have started calling it a data processor.

There are various ways in which computer can be defined but on the basis of its power the most

generalized and popular definition is -

“A computer is an electronic device which processes or manipulates the data strictly according to

the instructions given and produces meaningful result efficiently, effectively and reliably.”

“Computer can be defined as any machine, which can accept data, in prescribed form, process the

data and supply the result of processing in a specified format as information or as signals to

control automatically some further machine or process.”

- Dictionary of Computers – Penguin

Evolution of computers

Like civilizations, computers have also evolved over a period of time. Some of the important

stages of computer evolution are listed below:

Abacus is considered the earliest calculating device invented around 600 B.C., it is a rack of

beads used to add or subtract by positioning the beads correctly.

In 1642, Blaise Pascal invented first mechanical adding machine. The innovation and

invention continued according to the needs of people.

In 1822, a Professor of Cambridge University, Charles Babbage Known as father of computer,

invented “Difference Engine” which can produce reliable tables, as at that time mathematical

and statistical tables were prepared by the clerks which consumed lot of precious time and

was also very much prone to errors.

In 1942, he designed new machine “Analytical Engine” which was planned to be fully

automatic and capable of performing all basic arithmetic calculations. Somehow this machine

was not produced. But his idea gave most basic fundamentals of computer design.

In 1937, Haward Aiken of Harvard University, in collaboration with IBM developed “Mark I”

the punch card operated machine which could perform all the arithmetic calculations.

In 1943, ENIAC (Electronic Numerical Integrator and Calculator) was developed by a design

team headed by Professor Prosper Eckert and John Mauchly of Moore College of

Engineering, University of Pennsylvania. ENIAC was very complex to be programmed but it

was capable of performing calculations more than 200 times of Mark I.

In 1946, Professor Jon Von Neumann developed EDAVC (Electronic Discrete Variable

Automatic Computer). This computer stored the data and instructions in sequence, in memory

in the binary form (0 & 1). For this reason, modern computers are known as digital computers.

UNIVAC (Universal Automatic Computer) was first digital computer installed in Census

Bureau in 1951. By this time evolution was carried out at different places, but IBM

(International Business Machine) came out first and produced machines for business.

Computer Generations

Generation Years Switching

Device

Storage

Device

Switching

Time

MTBF Software Application

First 1949-

1955

Vacuum Tubes Acoustic delay

lines,

magnetic

drum. 1

Kbytes

memory

0.1 – 1

mille

second

30

minutes

to 1 Hr

Machine

and

assembly

languages.

Simple

monitors.

Mostly scientific.

Later simple

business systems.

Second 1956-

1965

Transistors Magnetic core

main memory,

tapes and disk

peripheral

memory. 100

Kb main

memory.

1 – 10

micro

second

About

10 Hrs

High level

languages,

FORTRAN,

COBOL,

Algol,

Batch

Operating

System

Extensive business

applications.

Engineering design

optimization

scientific research.

Third 1966-

1975

Integrated

Circuits(IC)

High speed

magnetic

cores. Large

disks (100

MB) 1MB

main memory.

0.1 – 1

micro

second

About

100 Hrs

FORTRAN

4, COBOL

68, PL/I

Timeshared

Operating

System

Database

management

system. Online

systems.

Fourth- I

Phase

1975-

1984

Large Scale

Integrated

Circuits

Microprocessors

Semiconducto

r memory.

Winches disk.

10 MB main

memory.

1000MB

disks.

10 – 100

nano

second

About

1000

Hrs

FORTRAN

&&, Pascal,

ADA,

COBOL 74,

Concurrent

Pascal

Personal

computers.

Distributed

systems. Integrated

CAD/CAM real

time control.

Graphic oriented

system.

Fourth – II

Phase

1985-

Present

Very Large

Scale Integrated

Semiconducto

r memory. 1

1 – 10

nano

About

10000

C, C++.

JAVA,

Simulation

visualization,

Circuits. Over 3

million

transistor per

chip

GB main

memory. 100

GB disk.

second Hrs PROLOG,

FP

Parallel computing,

Virtual reality,

Multimedia.

*MTBF - Mean time between failures of processor.

Characteristics of Computer

Speed

Computers work at an incredible speed. A powerful computer is capable of performing about 3-4

million simple instructions per second.

Accuracy

In addition to being fast, computers are also accurate. Errors that may occur can almost always be

attributed to human error (inaccurate data, poorly designed system or faulty instructions /

programs written by the programmer)

Diligence

Unlike human beings, computers are highly consistent. They do not suffer from human traits of

boredom and tiredness resulting in lack of concentration. Computers, therefore, are better than

human beings in performing voluminous and repetitive jobs.

Versatility

It means the capacity to perform completely different type of work. You may use your computer

to prepare payroll slips. Next moment you may use it for inventory management or to prepare

electric bills.

Storage

The Computer has an in-built memory where it can store a large amount of data. You can also

store data in secondary storage devices such as pen drive, DVD, CD, etc. which can be kept

outside your computer and can be carried to other computers.

No IQ

Computer is a dumb machine and it cannot do any work without instruction from the user. It

performs the instructions at tremendous speed and with accuracy. It is you to decide what you

want to do and in what sequence. So a computer cannot take its own decision as you can.

No Feeling

It does not have feelings or emotion, taste, knowledge and experience. Thus it does not get tired

even after long hours of work. It does not distinguish between users.

Uses of Computer

Education:

Getting the right kind of information is a major challenge as is getting information to make sense.

College students spend an average of 5-6 hours a week on the internet. Research shows that

computers can significantly enhance performance in learning. Students exposed to the internet say

they think the web has helped them improve the quality of their academic research and of their

written work. One revolution in education is the advent of distance learning. This offers a variety

of internet and video-based online courses.

Health and Medicine:

Computer technology is radically changing the tools of medicine. All medical information can

now be digitized. Software is now able to computer the risk of a disease. Mental health

researchers are using computers to screen troubled teenagers in need of psychotherapy. A patient

paralyzed by a stroke has received an implant that allows communication between his brain and a

computer; as a result, he can move a cursor across a screen by brainpower and convey simple

messages.

Science:

Scientists have long been users of computer. A new adventure among scientists is the idea of a

“collaboration”, an internet based collaborative laboratory, in which researchers all over the world

can work easily together even at a distance. An example is space physics where space physicists

are allowed to band together to measure the earth’s ionosphere from instruments on four parts of

the world.

Business:

Business clearly sees the interest as a way to enhance productivity and competitiveness. Some

areas of business that are undergoing rapid changes are sales and marketing, retailing, banking,

stock trading, etc. Sales representatives not only need to be better educated and more

knowledgeable about their customer’s businesses, but also must be comfortable with computer

technology. The internet has become a popular marketing tool. The world of cybercash has come

to banking – not only smart cards but internet banking, electronic deposit, bill paying, online

stock and bond trading, etc.

Recreation and Entertainment:

Our entertainment and pleasure-time have also been affected by computerization. For example:

i) In movies, computer generated graphics give freedom to designers so that special effects and

even imaginary characters can play a part in making movies, videos, and commercials.

ii) In sports, computers compile statistics, sell tickets, create training programs and diets for

athletes, and suggest game plan strategies based on the competitor’s past performance.

iii) In restaurants, almost every one has eaten food where the clerk enters an order by indicating

choices on a rather unusual looking cash register; the device directly enters the actual data into a

computer, and calculates the cost and then prints a receipt.

Government:

Various departments of the Government use computer for their planning, control and law

enforcement activities. To name a few – Traffic, Tourism, Information & Broadcasting,

Education, Aviation and many others.

Defense:

There are many uses computers in Defense such as:

1) Controlling UAV or unmanned air-crafts an example is Predator. If you have cable I would

recommend watching the shows “Future Weapons" and “Modern Marvels". The show future

weapon gives an entire hour to the predator.

2) They are also used on Intercontinental Ballistic Missiles (ICBMs) that uses GPS and

Computers to help the missile get to the target.

3) Computers are used to track incoming missiles and help slew weapons systems onto the

incoming target to destroy them.

4) Computers are used in helping the military find out where all their assets are (Situational

Awareness) and in Communications/Battle Management Systems.

5) Computers are used in the logistic and ordering functions of getting equipments to and around

the battlefield.

6) Computers are used in tanks and planes and ships to target enemy forces, help run the platform

and more recently to help diagnose any problems with the platforms.

7) Computers help design and test new systems.

Sports:

In today's technologically growing society, computers are being used in nearly every activity.

Recording Information

Official statistics keepers and some scouts use computers to record statistics, take notes and chat

online while attending and working at a sports event.

Analyzing Movements

The best athletes pay close attention to detail. Computers can slow recorded video and allow

people to study their specific movements to try to improve their tendencies and repair poor habits.

Writers

Many sportswriters attend several sporting events a week, and they take their computers with

them to write during the game or shortly after while their thoughts are fresh in their mind.

Scoreboard

While some scoreboards are manually updated, most professional sports venues have very

modern scoreboards that are programmed to update statistics and information immediately after

the information is entered into the computer.

Safety and Security

Computers have aided in the design of safety equipment in sports such as football helmets to

shoes to mouth guards. Computer becomes an integral part for security. Many security systems

have been developed and used through computers.

Classification of Computer

On the basis of Type of Data

Analog Computers

Analog Computer is a computing device that works on continuous range of values. The results

given by the analog computers will only be approximate since they deal with quantities that vary

continuously. It generally deals with physical variables such as voltage, pressure, temperature,

speed, etc.

Digital Computer

 A computer that performs calculations and logical operations with quantities represented as

digits, usually in the binary number system i.e. 1 and 0.

Hybrid Computer (Analog + Digital)

A combination of computers those are capable of inputting and outputting in both digital and

analog signals. A hybrid computer system setup offers a cost effective method of performing

complex simulations.

On the basis of Purpose

General Purpose Computers

The general purpose computers are designed to solve a large variety of applications through the

use of stored program/instructions in its internal storage. However, this versatility is achieved at

the expense of speed and efficiency of the computer. Most digital computers are general purpose

computers.

Special Purpose Computers

These are built to solve a specific problem. In these machines, the computer program for solving

the problem is built right into the computer. Their operations are specific and are usually made for

a single customer. Some examples are: automatic teller machine (ATM) for 24 hours banking,

industrial process system, etc.

On the basis of Size and Capacity

Super Computers

Large scientific and research laboratories as well as the government organizations have extra

ordinary demand for processing data which required tremendous processing speed, memory and

other services which may not be provided with any other category to meet their needs. Therefore

very large computers used are called Super Computers. These computers are extremely expensive

and the speed is measured in billions of instructions per seconds.

Supercomputers are mainly being used for whether forecasting, biomedical research, remote

sensing, aircraft design and other areas of science and technology. Examples of supercomputers

are CRAY YMP, CRAY2, NEC SX-3, CRAY XMP and PARAM from India.

Main Frame Computers

The most expensive, largest and the most quickest or speedy computer are called mainframe

computers. These computers are used in large companies, factories, organizations etc. the

mainframe computers are the most expensive computers; they cost more than 20 million rupees.

In these computers 150 users are able to work on one C.P.U. The mainframes are able to process

1 to 8 bits at a time. They have several hundreds of megabytes of primary storage and operate at a

speed measured in nano second.

Mini Computers

Mini computers are smaller than mainframes, both in size and other facilities such as speed,

storage capacity and other services. They are versatile that they can be fitted where ever they are

needed. Their speeds are rated between one and fifty million instructions per second (MIPS).

They have primary storage in hundred to three hundred megabytes range with direct access

storage device.

Micro Computers

These are the smallest range of computers. They were introduced in the early 70’s having less

storing space and processing speed. Micro computers of today are equivalent to the mini

computers of yesterday in terms of performing and processing. They are also called “computer of

a chip” because its entire circuitry is contained in one tiny chip. The micro computers have a wide

range of applications including uses as portable computer that can be plugged into any wall. It

includes:

Desktop Computer: a personal or micro-mini computer sufficient to fit on a desk.

Laptop Computer: a portable computer complete with an integrated screen and keyboard. It is

generally smaller in size than a desktop computer and larger than a notebook computer.

Palmtop Computer/Digital Diary /Notebook /PDAs: A hand-sized computer. Palmtops have no

keyboard but the screen serves both as an input and output device.

Computer Organization

Basic Computer Organization

Input Unit

The first step in any processing activity is providing data and the instructions for processing the

data. Since computer cannot understand human language, therefore this communication has to be

done in a language which computer can understand. The unit that perform this task of

communicating data and instructions to the computer is referred to as Input Unit. This data is in a

coded form (human understandable form), on an input medium and is read and translated by an

input device into a form which is understandable by computer i.e. binary form.

Some of the input devices are as follows:

The Mouse

Mouse is an input device that is used with personal computer. Earlier it rolls on a small ball but

now uses optical technology and has two or three buttons on the top. When you roll the mouse

across a flat surface the screen censors the mouse in the direction of mouse movement. The cursor

moves very fast with mouse giving you more freedom to work in any direction. It is easier and

faster to move through a mouse.

The Keyboard

This is the standard input device attached to all computers. The layout of keyboard is just like the

traditional typewriter of the type QWERTY. It also contains some extra command keys and

function keys. It contains a total of 101 to 104 keys. You have to press correct combination of

keys to input data. The computer can recognize the electrical signals corresponding to the correct

key combination and processing is done accordingly.

Tracker Balls

Track ball is similar to the upside - down design of the mouse. The user moves the ball directly,

while the device itself remains stationary. The user spins the ball in various directions to effect the

screen movements.

Scanners

Scanners are used to enter information directly in to the computers memory. This device works

like a Xerox machine. The scanner converts any type of printed or written information including

photographs into digital pulses, which can be manipulated by the computer.

Touch Pads

A touch pad is a laptop / palmtop device and responds to pressure.  Conjunction with a special

pen they can be used by graphic artists wishing to create original, digital artwork.

Light Pens

It is a pen shaped device used to select objects on a display screen. It is quite like the mouse (in its

functionality) but uses a light pen to move the pointer and select any object on the screen by

pointing to the object.

Joysticks

Many games require a joystick to play the game.  Any different types, but it may be worth

investing in a good quality one that is strong to withstand the rough treatment it will get from the

kids while they are playing the games and one that can respond to movement in three axis

directions.

Microphones

This micro phone is used to convert human speech into electric signals. The signal pattern is then

transmitted to a computer when it’s compared to a dictionary of patterns that have been

previously placed in a storage unit of computer. When a close match is found, the word is

recognized.

Web Cams

Small digital movie camera (a web cam) is mounted on the PC monitor to allow two way

communication involving not just text communication, but sound and video as well. 

Digital Cameras

It converts graphics directly into digital form. It looks like an ordinary camera, but no film is used

therein, instead a CCD (changed coupled Divide) Electronic chip in used. When light falls, on the

chip though the lens, it converts light waves into electrical waves.

Bar Code Reader

This device reads bar codes and coverts them into electric pulses to be processed by a computer.

A bar code is nothing but data coded in form of light and dark bars.

Output Unit

The data and instruction fed into the system through input unit go to memory of the computer.

The data is processed according to the instructions given and result is again stored in memory of

the computer in the form of binary digits 0 and 1. These results have to be communicated to the

outside world in human acceptable form. This function of communicating (through conversion)

the result of processing to the human being for decision making is performed by Output Unit.

Here are some most common output devices given below:

Visual Display Unit

The most popular input/output device is the Visual Display Unit (VDU). It is also called the

monitor. A Keyboard is used to input data and Monitor is used to display the input data and to

receive massages from the computer. A monitor has its own box which is separated from the main

computer system and is connected to the computer by cable. In some systems it is compact with

the system unit. It can be color or monochrome.

Printer

It is an important output device which can be used to get a printed copy of the processed text or

result on paper. There are different types of printers that are designed for different types of

applications. Depending on their speed and approach of printing, printers are classified as impact

and non-impact printers. Impact printers use the familiar typewriter approach of hammering a

typeface against the paper and inked ribbon. Dot-matrix printers are of this type. Non-impact

printers do not hit or impact a ribbon to print. They use electro-static chemicals and ink-jet

technologies. Laser printers and Ink-jet printers are of this type. This type of printers can produce

color printing and elaborate graphics.

Plotter

Plotters are used to print graphical output on paper. It interprets computer commands and makes

line drawings on paper using multicolored automated pens. It is capable of producing graphs,

drawings, charts, maps etc.

Audio Output: Speakers

The Audio output is the ability of the computer to output sound. Two components are needed:

Sound card – Plays contents of digitized recordings, Speakers – Attached to sound card.

Projector

An output device that takes the display of a computer screen and project a large version of it onto

a flat surface. Projectors are often used in meetings and presentations to help make sure everyone

in the room can view the presentation.

Storage Unit

Data and instructions entered into a computer system through input units have to be stored inside

the computer before actual processing starts. Similarly, results produced by the computer after

processing have to be kept somewhere inside the computer system before being passed on to an

output unit. Moreover, a computer must also preserve intermediate results for ongoing processing.

Storage unit of a computer system caters to all these need. It provides space for storing data and

instructions, intermediate results, and the results for output.

Storage unit of all computers is comprised of the following two types of storage:

Primary Storage

Primary storage, also known as main storage or memory, is used to hold pieces of program

instruction and data, intermediate result of processing, and recently produced result of those jobs

on which computer is currently working. These pieces of information are represented

electronically in the main memory chip’s circuitry and while it remains in the main memory, CPU

can access it directly at a very fast speed. It is volatile in nature i.e. as soon as the computer is

switched off or reset, the information hold by it is erased. Primary storage normally has limited

storage capacity and is very expensive. In modern computers it is made up of semiconductors.

It is of two types:

Random Access Memory (RAM)

Random Access Memory (RAM) is the best known form of computer memory. The Read and

write (R/W) memory of a computer is called RAM. The RAM is a volatile memory; it means

information written to it can be accessed as long as power is on. As soon as the power is off, it

can not be accessed. RAM holds data and processing instructions temporarily until the CPU needs

it. RAM is considered “random access” because you can access any memory cell directly if you

know the row and column that intersect at that cell. RAM is made in electronic chips made of so

called semiconductor material, just like processors and many other types of chips.

Read Only Memory (ROM)

One major type of memory that is used in PCs is called read - only memory or ROM for short.

ROM is a type of memory that normally can only be read, as opposed to RAM which can be both

read and written. There are two main reasons that read-only memory is used for certain functions

within the PC:

Permanence: The values stored in ROM are always there, whether the power is on or not. A ROM

can be removed from the PC, stored for an indefinite period of time, and then replaced, and the

data it contains will still be there. For this reason, it is called non-volatile storage.

Security: The fact that ROM cannot easily be modified provides a measure of security against

accidental (or malicious) changes to its contents.

Secondary Storage

Secondary Storage of a computer is also known as auxiliary storage, is used to take care of the

limitations of primary storage. That is, it supplements the limited storage capacity and volatile

characteristic of primary storage. This is much cheaper than the primary storage and can retain

information even when the computer switches off or resets. Secondary storage holds the program

instructions, data and information of those jobs on which the computer system is not currently

working but needs to hold them for processing later.

The different types of secondary storage devices are currently in use are as follows:

Arithmetic and Logic Unit

This unit performs the arithmetic and logical operations on the data and instructions supplied by

the input devices, under the command from the control unit. The basic arithmetic operations

performed are addition, subtraction, multiplication and division, which are built into the control

unit. In addition to arithmetic operations computer can perform logical operations as well e.g.

comparing two or more numbers or letters, making decision according to the defined criteria, etc.

this is a place where data is manipulated and the result are communicated to memory.

Control Unit

This is the most important unit in a computer system. It supervises the entire operation of a

computer system; it acts as a traffic policeman, which controls the traffic of data and electronic

signals between various units and components of computer. It instructs the input device when to

start and stop the input to memory, it transfer the input information from memory to arithmetic

and logic unit, it selects the proper operations to be carried out, it directs the memory unit when to

start and stop the transfer of information to output unit, etc. therefore the function of control unit

in a computer is to maintain order and direct the flow of operations in a proper manner. It acts like

central nervous system for various units of a computer.

Central Processing Unit

Control Unit, Arithmetic Logic Unit of a computer system are together known as Central

Processing Unit (CPU). The CPU is the brain of a computer system. In human body, the brain

takes all major decisions and other part of the body function as directed by the brain. Similarly, in

a computer system, all major calculations and comparisons takes place inside the CPU and the

CPU is responsible for activating and controlling the operations of other units of the computer

system.

Bibliography

Books of Reference:

Sinha P.K., Sinha Priti, “Computer Fundamentals”, BPB Publications, New Delhi, Fourth

Edition ( revised and reprinted), 2010.

Saini A.K., Kumar Pradeep, “Computer Applications in Management”, Anmol Publications

Pvt. Ltd., New Delhi, 2009.

Websites of Reference:

http://www. ecomputernotes.com

http://www.kkhsou.in

http://en.wikipedia.org

http://www.google.co.in/imghp?hl=en&tab=wi