Computer is an electronic device that accepts data as input, processes it, and produces output in a required format. It converts data into information through programs. A computer functions by inputting data, storing it, processing it, and outputting information. It has characteristics like accuracy, diligence, versatility, reliability, automation, large data storage capacity, and lack of intelligence. Computers are used in many fields like homes, medicine, entertainment, industry, education, government, banking, and science/engineering. The history of computers progressed from early mechanical devices like the abacus to modern electronic computers like ENIAC and UNIVAC.

1. Introduction to computer
computer is an electronic data processing device,
which accepts and store data input, processes the
data input, and generates the output in a required
format. This output is also referred as information.
Computer converts data into information with the
help of a set of programs.
During this transformation, a computer functions in
the following manner.
Figure : working of computer

2. Introduction to computer
• Input: computer input is whatever is entered or fed into
a computer system. Input can be supplied by a user by
using a keyboard, mouse or any another computer or
device such as a pen drive or CD-ROM.
• Store: A computer must store data so that it is available
for processing. Most computers have more than one
device for storing data.
• Process: Data is processed to generate information.
Data processing is the activity of performing calculations
on data or it is simply the rearrangement of data.
• Output: Computer output is information that has been
produced by a computer. Some examples of computer
include reports, documents, music, graphs and pictures.

3. Characteristics of computer
Some of the characteristics of computer are as
follows:
Accuracy
Computers perform calculations with 100%
accuracy. Errors may occur due to data
inconsistency or inaccuracy.
Diligence
A computer can perform millions of tasks or
calculations with the same consistency and
accuracy. It doesn’t feel any fatigue or lack of
concentration. Its memory also makes it
superior to that of human beings.
Versatility
Versatility refers to the capability of a

4. Characteristics of computer
Reliability
A computer is reliable as it gives consistent result
for similar set of data i.e., if we give same set of input
any number of times, we will get the same result.
Automation
Computer performs all the tasks automatically i.e. it
performs tasks without manual intervention.
Data storage Capacity
storage is a very important characteristic computers.
It can store any type of data such as images, videos,
text, audio and many others.
No Intelligence
A computer is a machine that has no intelligence to
perform any task. Each instruction has to computer. A
computer cannot take any decision on its own.

5. Applications of computers
There is hardly any field which is not influenced by computers.
Some of the application areas of computers are described below:
Home
Computers are used at homes for several purposes like
online bill payment, watching movies or shows at home, home
tutoring, social media access, playing games, internet access,
etc. They provide communication through electronic mail. They
help to avail work from home facility for corporate employees.
Computers help the student community to avail online
educational support.
Medical Field
Computers are used in hospitals to maintain a database of
patients’ history, diagnosis, X-rays, live monitoring of patients,
etc. Surgeons nowadays use robotic surgical devices to perform
delicate operations, and conduct surgeries remotely. Virtual
reality technologies are also used for training purposes. It also
helps to monitor the fetus inside the mother’s womb.

6. History of computers
In past computer did not exist in its present shape
, model, architecture and processing mechanism.
There were a lot of devices evolved for the
development of modern digital computers. The
gradual study on early to present device regarding
the development of computer is considered as
history of computer. The brief history of computer
can be discussed on the basis of following eras.
1.The pre-mechanical Era
2. The mechanical Era
3. The Electro-Mechanical Era
4. The Electronic Era.

7. Applications of computer
Entertainment
Computers help to watch movies online, play games
online; act as a virtual entertainer in playing games,
listening to music, etc. MIDI instruments greatly help
people in the entertainment industry in recording music
with artificial instruments. Videos can be fed from
computers to full screen televisions. Photo editors are
available with fabulous features.
Industry
Computers are used to perform several tasks in
industries like managing inventory, designing purpose,
creating virtual sample products, interior designing, video
conferencing, etc. Online marketing has seen a great
revolution in its ability to sell various products to
inaccessible corners like interior or rural areas. Stock
markets have seen phenomenal participation from
different levels of people through the use of computers.

8. Applications of computer
Education
Computers are used in education sector through online classes, online
examinations, referring e-books, online tutoring, etc. They help in
increased use of audio-visual aids in the education field.
Government
In government sectors, computers are used in data processing,
maintaining a database of citizens and supporting a paperless
environment. The country’s defense organizations have greatly
benefitted from computers in their use for missile development,
satellites, rocket launches, etc.
Banking
In the banking sector, computers are used to store details of
customers and conduct transactions, such as withdrawal and deposit of
money through ATMs. Banks have reduced manual errors and expenses
to a great extent through extensive use of computers.
Science and Engineering
Computers with high performance are used to stimulate dynamic
process in Science and Engineering. Supercomputers have numerous
applications in area of Research and Development (R&D). Topographic
images can be created through computers. Scientists use computers to
plot and analyze data to have a better understanding of earthquakes.

9. 1. The pre-mechanical Era
The pre-mechanical age is the earliest age of
information technology. It can be defined as the time
between 3000B.C and 1450B.C
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;

10. Napier’s Bone:
Napier’s Bone is manually-operated calculating
device created by John Napier in 1617. It is used for
calculating of products and quotients if numbers.
Engineers till 1970s used it and latter it was replaced
by pocket calculators.
Slide Rule:
William oughtred developed the slide rule in 1622.
The slide rule uses two logarithmic scales to allow
rapid multiplication and division of numbers.
Multiplication and division is calculated by sliding
these two scales. More Elaborated slide rules allow
other calculations, such as square roots,
Exponentials, logarithms and trigonometric functions.

11. The mechanical Era
The mechanical age is when we first start to see connections between our current
technology and its ancestors. The mechanical age can be defined as the time
between 1450 and 1840.
Pascal’s machine:
In 1642, french mathematician Blaise pascal invented first mechanical calculator
named Pascaline to help his father that could add and subtract the number by using
the series of eight rotating wheels. It has the calculating capability up to
99,99,99,999. A programming in 1960 to honor Blaise Pascal for his great
contribution.
Leibnitz’s Calculating Machine
In 1671, modifying the Pascaline machine, German Mathematician developed a
device called Leibniz’s calculating machine. It could add, subtract, multiply, divide
and calculationg even square roots.
Leibnitz’s Calculating Machine
In 1671, modifying the Pascaline machine, German Mathematician developed a
device called Leibniz’s calculating machine. It could add, subtract, multiply , divide,
and calculate even square roots.
Analytical Engine
Charles Babbage is known as the father of computer science. At first binary
system was imagined by Francis Bacon in 1623. Later this system was practically
used by Charles Babbage in 1832 in his Analytical Engine. He also gave basic idea of
input, processing and output. Therefore, he is known as the father of computer
science.

12. The Electro-Mechanical Era
Census Tabulating Machine:
Herman Hollerith Develop the tabulating machine. The
tabulating machine was an electrical device designed to
assist in summarizing information and, later accounting.
The machine was developed to help process data for the
1890 U.S Census.
Howard Mark I
Mark I is an electromechanically operated computer
made by professor Howard Aiken in 1937. This machine
used punched cards which charles Babbage also used
for his Analytical Engine. This machine was 51 feet long,
3 feet wide and 8 feet height. It has 18000 vacuum
tubes, 750,000 parts and cable connection about 500
miles long. It took 1 second for 3 mathematical addition
and 4.5 seconds for multiplication.

13. The Electronic Era
ENIAC:
ENIAC (Electronic Numerical Integrator and Calculator )
was developed by Professor J.P Eckert and Jhon W.
Mauchly. It had the storage concept developed in it. It is an
electronic calculator. It is very huge machine and it has
various switches to feed the instruction. It can perform
multiplication in 3000th
of second. It has 18,000 vacuum
tubes and 70,000 registers.
EDSAC
M.V Wilkes was the professor at Cambridge University
invented EDSAC( Electronic Delay Storage Automation
Computer). According to the prior suggestion given by
Hungarian mathematician Dr. Jhon Von Neumann this was
the first effective, electronic computer, having stored
program concept.

14. The Electronic Era
EDVAC
EDVAC (Electronic Discrete Variable Automatic Computer)
was developed by professor J.P Eckert and Jhon W.
Mauchly in 1952. This computer operated electronically
and used to store the data and instruction as well.
UNIVAC-1
After the indentation of EDVAC, ENIAC etc, Jhon W.
Mauchly and J.P. Eckert got encouraged and opened own
company and started to design UNIVAC-1 (Universal
Automatic Computer) UNIVAC-II was commercial purpose
machine and used in Census Bureau of statistics. Later,
IBM company developed better and cheaper computers
series in 1954-55. Since then, IBM is one of the leading
computers manufacturing company.

15. Generation of computers
• The development of computer
systems is normally discussed as the
development over different
generations.
• With the succession of different
generations, came the advancement
in computer technology.
• Let us now discuss the development
in Computer Technology over the
different generations.

16. First Generation Cimputer
• The period 1940 to 1956, roughly considered
as the First Generation of Computer.
• The first generation computers were
developed by using vacuum tube or
thermionic valve machine.
• The input of this system was based on
punched cards and paper tape; however, the
output was displayed on printouts.
• The first generation computers worked on
binary-coded concept (i.e., language of 0-
1). Examples: ENIAC, EDVAC, etc.

17. Second Generation Computer
• The period 1956 to 1963 is roughly
considered as the period of Second
Generation of Computers.
• The second generation computers were
developed by using transistor technology.
• In comparison to the first generation, the
size of second generation was smaller.
• In comparison to computers of the first
generation, the computing time taken by
the computers of the second generation
was lesser.

18. Third Generation Computer
• The period 1963 to 1971 is roughly considered as the period
of Third Generation of computers.
• The third generation computers were developed by using the
Integrated Circuit (IC) technology.
• In comparison to the computers of the second generation,
the size of the computers of the third generation was smaller.
• In comparison to the computers of the second generation,
the computing time taken by the computers of the third
generation was lesser.
• The third generation computer consumed less power and also
generated less heat.
• The maintenance cost of the computers in the third
generation was also low.
• The computer system of the computers of the third
generation was easier for commercial use.

19. Fourth Generation
Computer
• The period 1972 to 2010 is roughly considered as the
fourth generation of computers.
• The fourth generation computers were developed by
using microprocessor technology.
• By coming to fourth generation, computer became
very small in size, it became portable.
• The machine of fourth generation started generating
very low amount of heat.
• It is much faster and accuracy became more reliable.
• The production cost reduced to very low in
comparison to the previous generation.
• It became available for the common people as well.

20. Fifth Generation computer
• The period 2010 to till date and beyond, roughly
considered as the period of fifth generation of
computers.
• By the time, the computer generation was being
categorized on the basis of hardware only, but the fifth
generation technology also included software.
• The computers of the fifth generation had high
capability and large memory capacity.
• Working with computers of this generation was fast
and multiple tasks could be performed simultaneously.
• Some of the popular advanced technologies of the fifth
generation include Artificial intelligence, Quantum
computation, Nanotechnology, Parallel processing, etc.

21. Classification of computers
1.Classification on the Basis of working
principle
2. Classification on the Basis of power
and size
3. Classification on the Basis of Brand

22. Classification on the Basis of Working Principle
1. 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 like laptops,
desktops including smart phones that we use at home or office are digital
computers.
• Advantages of digital computers:
• It allows you to store a large amount of information and to retrieve it easily
whenever you need it.
• You can easily add new features to digital systems more easily.
• Different applications can be used in digital systems just by changing the
program without making any changes in hardware
• The cost of hardware is less due to the advancement in the IC technology.
• It offers high speed as the data is processed digitally.
• It is highly reliable as it uses error correction codes.
• Reproducibility of results is higher as the output is not affected by noise,
temperature, humidity, and other properties of its components.

23. Analog computer
An analog computer is a computer which is used to process analog
data. Analog computers store data in a continuous form of physical
quantities and perform calculations with the help of measures. It is
quite different from the digital computer, which makes use of
symbolic numbers to represent results. Analog computers are
excellent for situations which require data to be measured directly
without converting into numerals or codes. Analog computers,
although available and used in industrial and scientific applications
like control systems and aircraft, have been largely replaced by
digital computers due to the wide range of complexities involved
Advantages of using analog computers:
• Analog computers are based on continuously varying data.
• These computers measures only natural or physical values.
• Analog computers are used for special purpose.
• Accuracy of these computers is very low because of noise and less
filtering facility.
• These computers are faster that digital computers.

24. Hybrid Computer
Hybrid computer has features of both analogue and digital
computer. It is fast like an analog 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:
• Its computing speed is very high due to the all-parallel configuration
of the analogue subsystem.
• It produces precise and quick results that are more accurate and
useful.
• It has the ability to solve and manage big equation in real-time.
• It helps in the on-line data processing.

25. 2. Classification on the Basis of Power and size
1.Super computer
Supercomputers are one of the fast computers currently
available. Supercomputers are very expensive and are employed
for specialized applications that require immense amount of
mathematical calculations.
For example, weather forecasting, scientific simulations,
(animated) graphics, fluid dynamic calculations, nuclear energy
research, electronic design, and analysis of geological data.
2. Mainframe computer
Mainframe is very large in size and is an expensive computer
capable of supporting hundreds or even thousands of users
simultaneously. Mainframe executes many programs
concurrently and supports many simultaneous execution of
programs. These are mainly used by insurance companies,
banks, airlines, ticket reservation system etc. IBM360, IBM370,
IBM1401 are examples of mainframe computer.

26. Classification on the Basis of Power and size
3. Mini computers
A Minicomputer is also referred to as Mini, is a class of small computing
devices. It was developed in the mid of 1960s. It has all the features and
functionality of a large computer, but it is smaller in size. It lies in the
middle range of computing systems, between the mainframe and
microcomputer as it is smaller than the mainframe and larger than a
microcomputer. The Minicomputers are multiprocessing computer. It
consists of two or more processors.
The Minicomputers are used in an organization for basic tasks such as
billing, accounting, and inventory management.
4. Micro Computers
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 first
microcomputer was built with 8-bit microprocessor chips. The common
examples of microcomputers include laptops, desktop computers,
personal digital assistant (PDA), tablets, and smart phones.
Microcomputers are generally designed and developed for general usage
like browsing, searching for information, internet, MS Office, social media,
etc.

27. What is workstations?
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. In terms of storage
capacity and speed, it comes between a
personal computer and minicomputer. Work
stations are generally used for specialized
applications such as desktop publishing,
software development, and engineering
designs.

28. 3. Classification on the Basis of
Brand
1.IBM PC
It stands for international Business machine Personal computer and
developed by IBM company. It is Commonly known as the IBM PC. IBM
company is the First company that manufactured personal computers.
IBM computers use CISC (Complex Instruction set Computing) CPUs. It
uses the Intel chips for its PCs and relied to Microsoft for operating
system. When the personal computer hit the market it was a major hit
and IBM gained a strong power in electronic computers. IBM PCs are
expensive and powerful computers than IBM compatibles.
2. IBM compatible Computer
Phoenix Technologies went through published documentation of BIOS
used in IBM PCs . They designed BIOS of their own which could be used
with IBM computers. Many manufacturers jumped in and started making
their own IBM compatible computers . These computers are cheaper than
IBM and are made for the general people.
3.Apple/Macintosh computers
All the computers manufactured by the apple cooperation are known as
Apple/ Macintosh computers. These computers use their own software
and hardware and are totally different than that of IBM computers, In
terms of both hardware and software. Software developed for Apple
computer can’t run on IBM computers.