Unit – 1
Introduction to Computer System
Definition of Computer with Architecture &
its Features.
Types of Computer
Classification of Micro Computer
History of Computer
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Types of Computer
We can categorize computer by two ways:
data handling capabilities and size.
On the basis of data handling capabilities,
The computer is of three types:
1. Analog Computer
2. Digital Computer
3. Hybrid Computer
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1) Analog Computer
Analog 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.
The analog computers measure the continuous changes in
physical quantity and generally render output as a reading on a
dial or scale.
Analog 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.
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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.
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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. 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.
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Classification of computers based on size & type
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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.
2) Mainframe computer
Mainframe computers are designed to support hundreds or
thousands of users Concurrently.
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.
3) Miniframe computer
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 the tasks such as billing, accounting and inventory
management.
4) Workstation
Workstation is a single user computer that is designed for
technical or scientific applications.
It has faster microprocessor, 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.
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5) Micro computer
Microcomputer is also known as 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.
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Classification of Microcomputers?
There are many different types of microcomputers, such as
personal computers, tablet computers, smartphones etc . Any
type of computer or device that has a microprocessor chip is a
microcomputer.
The term personal computer covers many different types of
devices when describing microcomputers. The following is a list
of different types of microcomputers:
1. Desktop computer
2. Notebook or laptop computer
3. Hand Held computer
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Classification of Microcomputers?
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Classification of Micro computers?
Desktop:
Desktop Computer or Personal Computer (PC) is the most
common type of microcomputer.
It is a stand-alone machine that can be placed on the desk.
Externally, it consists of three units—keyboard, monitor, and a
system unit containing the CPU, memory, hard disk drive, etc.
It is not very expensive and is suited to the needs of a single user
at home, small business units, and organizations.
Apple, Microsoft, Dell and Lenovo are some of the PC
manufacturers.
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Classification of Micro computers?
Notebook Computers or Laptop resemble a notebook.
They are portable and have all the features of a desktop
computer.
The advantage of the laptop is that it is small in size (can be
put inside a briefcase), can be carried anywhere, has a
battery backup and has all the functionality of the desktop.
Laptops can be placed on the lap while working (hence the
name).
Laptops are expensive than the desktop machines.
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Classification of Micro computers?
Handheld Computer or Personal Digital Assistant (PDA) is a
small computer that can be held on the top of the palm.
It is small in size. Instead of the keyboard, PDA uses a pen or a
stylus for input.
PDAs do not have a disk drive. They have a limited memory and
are less powerful.
PDAs can be connected to the Internet via a wireless connection.
Casio and Apple are some of the manufacturers of PDA.
Over the last few years, PDAs have merged into mobile phones to
create smart phones.
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HISTORY OF COMPUTER
Calculating Machines ABACUS was the first mechanical
calculating device for counting of large numbers.
The word ABACUS means calculating board.
It consists of bars in horizontal positions on which sets of beads
are inserted.
The horizontal bars have 10 beads each, representing units, tens,
hundreds, etc
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HISTORY OF COMPUTER
Napier’s Bones was a mechanical device built for the
purpose of multiplication in 1617 A.D. by an English
mathematician John Napier.
Slide Rule was developed by an English mathematician
Edmund Gunter in the 16th century. Using the slide rule,
one could perform operations like addition, subtraction,
multiplication and division. It was used extensively till
late 1970s. Figure below shows a slide rule.
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HISTORY OF COMPUTER
Pascal’s Adding and Subtraction Machine was developed
by Blaise Pascal. It could add and subtract. The machine
consisted of wheels, gears and cylinders.
Leibniz’s Multiplication and Dividing Machine was a
mechanical device that could both multiply and divide. The
German philosopher and mathematician Gottfried Leibniz
built it around 1673.
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HISTORY OF COMPUTER
Punch Card System was developed by Jacquard to control
the power loom in 1801.
He invented the punched card reader that could recognize
the presence of hole in the punched card as binary one and
the absence of the hole as binary zero.
The Os and 1s are the basis of the modern digital computer.
A punched card is shown in Figure below:
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HISTORY OF COMPUTER
Babbage’s Analytical Engine An English man Charles
Babbage built a mechanical machine to do complex
mathematical calculations, in the year 1823. The machine
was called as difference engine. Later, Charles Babbage and
Lady Ada Lovelace developed a general-purpose calculating
machine, the analytical engine. Charles Babbage is also
called the father of computer.
Hollerith’s Punched Card Tabulating Machine was
invented by Herman Hollerith. The machine could read the
information from a punched card and process it
electronically.
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Reference:
https://www.javatpoint.com/types-of-computer
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