1.2 WHAT IS A COMPUTER?

 Computer is an electronic device which capable of

solving problems and manipulating data.
 Computer can be defined in terms of its functions. It
can
I. accept data.
II. store data.

III. process data as desired by doing some mathematical

and logical operations.
IV. retrieve the stored data as and when required.

V. print the result in desired format.

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1.3 CHARACTERISTICS OF
COMPUTER
1- Speed
 Computer can work very fast .

 Computer can perform millions of instructions and even

more per second.
 The speed of computer in terms of microsecond (10-6 part
of second) or nanosecond (10-9 part of a second).
 The speed of microprocessors, called the clock speed, is
measured in megahertz.
 A microprocessor that runs at 200 MHz executes 200
million cycles per second .

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2- Accuracy
 The degree of accuracy of computer is very high and every
calculation is performed with the same accuracy.
 The accuracy level is determined on the basis of design of
computer.
 The errors in computer are due to human and inaccurate
data.
3- Diligence
 A computer is a lack of concentration.
 It can work for hours without creating any error
 Due to this capability it overpowers human being in
routine type of work.

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4- Versatility
 It means the capacity to perform completely
different type of work.
5-Power of Remembering
 Any amount of information can be stored in
computer and recalled as long as you require it,
for any numbers of years.
 It depends entirely upon you how much data you
want to store in a computer and when to lose or
retrieve these data.

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6- No IQ (intelligence quotient)
 Computer is a dumb machine and it cannot do any work
without instruction from the user and it cannot take its
own decision as you can .
7- No Feeling
 It does not have feelings ,
 it does not get tired even after long hours of work.
8- 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 floppies, CDs Flash Memory which can be kept
outside your computer and can be carried to other
computers.

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Advantages and Disadvantages
of Using Computers
Advantages of Disadvantages of
Using Computers Using Computers

Speed Health Risks

Reliability Violation of Privacy

Consistency Public Safety

Storage Impact on Labor Force

Communications Impact on Environment

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1.4 HISTORY OF COMPUTER

 1-Calculating Machines
The first calculating device called
ABACUS was developed by the
Egyptian and Chinese people.
3000 BC
 Fig. 1.2: Abacus Computer

 2- Napier’s bones
English mathematician John Napier
built a mechanical device for the
purpose of multiplication (1617)

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 3 -Slide Rule English mathematician Edmund
Gunter developed the slide rule. This machine
could perform operations like addition,
subtraction, multiplication, and division. It was
widely used in Europe in 16th century. (1623)
 4- Pascal's Machine a machine consisted of
wheels, gears and cylinders, that could add and
subtract . (1645)
 5-Joseph Jacquard: Jacquard’s Loom,
the punched card, first stored program-
metal cards. (1801)

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 6- Babbage’s Analytical Engine
 Charles Babbage (father of computer) built a
mechanical machine to do complex mathematical
calculations. (1822-1842)
 7-Mechanical and Electrical Calculator
 Mechanical calculator was developed to perform all
sorts of mathematical calculations. Later mechanical
calculator was developed to the electrical calculator.
 8-Modern Electronic Calculator
 At first made quite bulky then transistors.
 It can do all kinds of mathematical computations and
store some data permanently.
 It is size too small.

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1.5 COMPUTER GENERATIONS
 1-First Generation Computers
 First generation computers used Thermion valves. These
computers were large in size and writing programs on
them was difficult.
 Some of the computers of this generation were:
ENIAC : It was named Electronic Numerical Integrator And
Calculator (ENIAC). Today your favorite computer is many times
as powerful as ENIAC, still size is very small.
EDVAC: It stands for Electronic Discrete Variable Automatic
Computer and was developed in 1950. The advantages is storing
and doing logical decision internally.
 Other Important Computers of First Generation:
EDSAC: ( Electronic Delay Storage Automatic Computer )
UNIVAC-1.

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 Limitations of First Generation Computer:
Some drawbacks of first generation of computers:
 The operating speed was quite slow.

 Power consumption was very high.

 It required large space for installation.

 The programming capability was quite low.

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 2-Second Generation Computers
 Around 1955 a device called Transistor replaced the bulky
electric tubes in the first generation computer. They have no
filament and require no heating. Manufacturing cost was also
very low. Thus the size of the computer got reduced
considerably.
 It is in the second generation that the concept of Central
Processing Unit (CPU), memory, programming language and
input and output units were developed. The programming
languages such as COBOL, FORTRAN were developed
during this period. Some of the computers of the Second
Generation were:
 IBM 1620: Its size was smaller as compared to First Generation computers and
mostly used for scientific purpose.
 IBM 1401: Its size was small to medium and used for business applications.
 CDC 3600: Its size was large and is used for scientific purposes.

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 3 Third Generation Computers was
introduced in 1964. They used Integrated Circuits
(ICs). Some of the computers developed during
this period were: IBM-360, ICL-1900, IBM-370,
and VAX-750.
 Higher level language such as BASIC was
developed during this period.
 Computers of this generations were small in size,
low cost, large memory and processing speed is
very high.

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 4-Fourth Generation Computers ( present day
computers) . It uses large scale Integrated Circuits
(LSIC) built on a single silicon chip called
microprocessors. Due to the development of
microprocessor it is possible to place computer’s central
processing unit (CPU) on single chip. These computers
are called microcomputers.
 5-Fifth Generation Computer was introduced in
1990s . The speed is extremely high and it can perform
parallel processing. The concept of Artificial intelligence
has been introduced to allow the computer to take its own
decision. It is still in a developmental stage.

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Computer Generations

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Computer Generations

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Computer Generations

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Computer Generations

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1.7 TYPES OF COMPUTERS

 1-Microcomputer.
 2-Mini Computer.
 3-Mainframes.
 4-Supercomputer.

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*Microcomputers :

 Microcomputer is at the lowest end of the

computer range in terms of speed and storage
capacity. Its CPU is a microprocessor. The most
common application of personal computers (PC)
is in this category. The PC supports a number of
input and output devices. Examples of
microcomputer are IBM PC, PC-AT

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*Mini Computer:
 The mini computer is used in multi-user
system in which various users can work at
the same time. This type of computer is
generally used for processing large volume
of data in an organization. They are also
used as servers in Local Area Networks
(LAN).

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*Mainframes:
 These types of computers are generally 32-bit
microprocessors. They operate at very high
speed, have very large storage capacity and can
handle the work load of many users. They are
generally used in centralized databases. They are
also used as controlling nodes in Wide Area
Networks (WAN).
 Example of mainframes are DEC, ICL and IBM
3000 series.

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*Supercomputer:
 They are the fastest and most expensive
machines. They have high processing speed
compared to other computers. They have
also multiprocessing technique. One of the
ways in which supercomputers are built is by
interconnecting hundreds of
microprocessors.

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 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.

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