What is Computer?

A computer is a programmable electronic device that accepts raw data as input and
processes it with a set of instructions (a program) to produce the result as output. The term
"computer" is derived from the Latin word "computare" which means to calculate.

Classifications of Computer based on the following criteria:

Based on CAPACITY

1. Micro Computer

It is a single-user computer which has less speed and storage capacity than the other types. It
uses a microprocessor as a CPU. The common examples of microcomputers include laptops,
desktop computers, personal digital assistant (PDA), tablets, and smartphones.

2. Mini Computer

Mini-computers are also known as "Midrange Computers." So, they are generally used by small
businesses and firms. For example, the admission department of a University can use a Mini-
computer for monitoring the admission process.

3. Mainframe Computer

It is also a multi-user computer capable of supporting thousands of users simultaneously. They

are used by large firms and government organizations to run their business operations. For
example, Banks, universities, and insurance companies use mainframe computers to store the
data of their customers, students, and policyholders, respectively.

4. Super Computer

Super-computers are the fastest and most expensive computers among all types of computers.
For example, NASA uses supercomputers for launching space satellites and monitoring and
controlling them for space exploration.

5. Work stations

It is a single-user computer. Although it is like a personal computer, it has a more powerful

microprocessor and a higher-quality monitor than a microcomputer. Work stations are
generally used for specialized applications such as desktop publishing, software development,
and engineering designs.

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Based on DATA HANDLING:

1) Analogue Computer

Analogue computers are designed to process the analogue data. Analogue data is continuous
data that changes continuously and cannot have discrete values such as speed, temperature,
pressure and current. Speedometer and mercury thermometer are examples of analogue
computers.

2) Digital Computer

Digital computer is designed to perform calculations and logical operations at high speed. It
accepts the raw data as digits or numbers and processes it with programs stored in its memory
to produce output. All modern computers like laptops and desktops that we use at home or
office are digital computers.

3) Hybrid Computer

Hybrid computer has features of both analogue and digital computer. It is fast like analogue
computer and has memory and accuracy like digital computers. It can process both continuous
and discrete data. For example, a processor is used in petrol pumps that converts the
measurements of fuel flow into quantity and price.

HISTORY OF COMPUTERS

The first counting device was used by the primitive people. They used sticks, stones and
bones as counting tools. 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. An image of this tool is shown below;

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 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. An image of this tool is shown below;

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. See the following image;

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.

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 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.

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.

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Generations of Computer

1. FIRST GENERATION
1. 1946-1959 is the period of first generation computer.
2. J.P.Eckert and J.W.Mauchy invented the first successful electronic computer called
ENIAC, ENIAC stands for “Electronic Numeric Integrated And Calculator”.
 Few Examples are:
1. ENIAC
2. EDVAC
3. UNIVAC
4. IBM-701
5. IBM-650
 Advantages:
1. It made use of vacuum tubes which are the only electronic component available
during those days.
2. These computers could calculate in milliseconds.
 Disadvantages:
1. These were very big in size, weight was about 30 tones.
2. These computers were based on vacuum tubes.
3. These computers were very costly.
4. It could store only a small amount of information due to the presence of
magnetic drums.
5. As the invention of first generation computers involves vacuum tubes, so
another disadvantage of these computers was, vacuum tubes require a large
cooling system.
6. Very less work efficiency.
7. Limited programming capabilities and punch cards were used to take inputs.
8. Large amount of energy consumption.
9. Not reliable and constant maintenance is required.

2. SECOND GENERATION
1. 1959-1965 is the period of second-generation computer.
2. 3.Second generation computers were based on Transistor instead of vacuum tubes.
 Few Examples are:
1. Honeywell 400
2. IBM 7094
3. CDC 1604
4. CDC 3600
5. UNIVAC 1108
 Advantages:
1. Due to the presence of transistors instead of vacuum tubes, the size of electron
component decreased. This resulted in reducing the size of a computer as
compared to first generation computers.

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 2. Less energy and not produce as much heat as the first genration.
3. Assembly language and punch cards were used for input.
4. Low cost than first generation computers.
5. Better speed, calculate data in microseconds.
6. Better portability as compared to first generation
 Disadvantages:
1. A cooling system was required.
2. Constant maintenance was required.
3. Only used for specific purposes.

3. THIRD GENERATION
1. 1965-1971 is the period of third generation computer.
2. These computers were based on Integrated circuits.
3. IC was invented by Robert Noyce and Jack Kilby In 1958-1959.
4. IC was a single component containing number of transistors.
 Few Examples are:
1. PDP-8
2. PDP-11
3. ICL 2900
4. IBM 360
5. IBM 370
 Advantages:
1. These computers were cheaper as compared to second-generation computers.
2. They were fast and reliable.
3. Use of IC in the computer provides the small size of the computer.
4. IC not only reduce the size of the computer but it also improves the performance
of the computer as compared to previous computers.
5. This generation of computers has big storage capacity.
6. Instead of punch cards, mouse and keyboard are used for input.
7. They used an operating system for better resource management and used the
concept of time-sharing and multiple programming.
8. These computers reduce the computational time from microseconds to
nanoseconds.
 Disadvantages:
1. IC chips are difficult to maintain.
2. The highly sophisticated technology required for the manufacturing of IC chips.
3. Air conditioning is required.

4. FOURTH GENERATION
1. 1971-1980 is the period of fourth generation computer.
2. This technology is based on Microprocessor.
3. A microprocessor is used in a computer for any logical and arithmetic function to be
performed in any program.

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 4. Graphics User Interface (GUI) technology was exploited to offer more comfort to
users.
 Few Examples are:
1. IBM 4341
2. DEC 10
3. STAR 1000
4. PUP 11
 Advantages:
1. Fastest in computation and size get reduced as compared to the previous
generation of computer.
2. Heat generated is negligible.
3. Small in size as compared to previous generation computers.
4. Less maintenance is required.
5. All types of high-level language can be used in this type of computers.
 Disadvantages:
1. The Microprocessor design and fabrication are very complex.
2. Air conditioning is required in many cases due to the presence of ICs.
3. Advance technology is required to make the ICs.

5. FIFTH GENERATION
1. The period of the fifth generation in 1980-onwards.
2. This generation is based on artificial intelligence.
3. The aim of the fifth generation is to make a device which could respond to natural
language input and are capable of learning and self-organization.
4. This generation is based on ULSI (Ultra Large Scale Integration) technology resulting
in the production of microprocessor chips having ten million electronic components.
 Few Examples are:
1. Desktop
2. Laptop
3. NoteBook
4. UltraBook
5. Chromebook
 Advantages:
1. It is more reliable and works faster.
2. It is available in different sizes and unique features.
3. It provides computers with more user-friendly interfaces with multimedia
features.
 Disadvantages:
1. They need very low-level languages.
2. They may make the human brains dull and doomed.

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