cottonseedfearnotElectronique - Appareils

7 nov. 2013 (il y a 7 années et 11 mois)

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Computers can be classified on the basis of:

Technology they are using.

Processing speed and Storage capacity.(Size
and Functions)

Purpose for which they are used.

On Basis of Technology

of Data Processing for which they are
designed. Following
type of
computer can exist

Analog Computers
: These computers operate on the data which are
continuously varying with respect to same physical quantity.
Continuous data can be obtained through measurements.


A speedometer measures speed of an automobile


Analog computing systems are frequently used to control
processing such as those found in oil refinery where flow
measurements and temperature measurements are important

It is a special purpose machine designed for some scientific and
technical applications .It is generally used in chemical plants for
monitoring temperatures, pressures, voltage, etc


Analog Computers operate on physical quantity that has continuous
signals that is temperature, pressure, speed, current etc. Processing
is continuous and produced output continuously .It produce limited
precision thus accuracy is not significant and speed is usually very
high. They are less expensive and require less programming efforts.

Digital Computers

computers manipulate discrete data and can perform
arithmetic and logical operations .The data which are
countable and discrete data (digits) as 0 and 1.

Total no of students in the class, No of patients in

computers are used in commercial and
administrative applications and for mathematical


Digital computer is a machine that accepts data and
produces information in discrete

produce high level of accuracy which is very significant.
They are thus, high precision, lower speed machine as
compared to analog computers.

They are expensive and require significant programming
efforts and is difficult to program. It is used for general and
specific purposes.

Contd…Hybrid Computers

It is the combination of analog and digital
computers .In hybrid computers some
calculations are performed in the analog
portion of the computer and some are
performed in digital portion of computer.


Such computers are used for scientific
applications and Industrial control processes.

On Basis of Processing Speed and Storage capacity


Microcomputer is a small sized and inexpensive
computer originated in late 1970’s .First Microcomputer was build
with 8 bit microprocessor chip now 16 bit ,32 bit ,64 bit
microcomputer has arrived .The speed of CPU is more than 100kilo
instructions per second(kips). A micro computer is a device which
must be capable of :

Receiving inputs in the form of data and instruction in the input

Performing arithmetic and Logical computation in ALU .In
Microcomputers this task together with device controlling is
performed by the microprocessor.

Storage of data and Instruction using memories.

Displaying the results computed by microprocessor to output device

Directly or indirectly controlling the devices that perform the above
mentioned task

Microcomputers have been considered to be of
two types:



Personal Computers(PC)

Personal Computer is a small single user computer based on a
microprocessor .A Pc has several chips (CPU chip, RAM chip , ROM chip ,I/O
handling chips etc.) neatly assembled on main circuit board called as system
board or mother board. They are designed as single user but is very
common to link them to form a network.

Two commonly used models of PC’s are Desktop model and Tower Model.
In Desktop model, monitor is kept on top of system unit whereas in Tower
model, system unit stands by the side of monitor.

Types of PC’s


Workstation is a powerful single user computer
.It is like a personal computer but has more
powerful microprocessor. It is used for
Engineering applications (CAD/CAM), Desktop
publishing (DTP), software development,
Multimedia, and other scientific problems. In
networking workstations refers to any
computer connected to a local area network


A minicomputer is a small general purpose computer with computing
power larger than a microcomputer .Their capacity lies between
microcomputers and mainframe computers.

They are usually designed to handle multiple client requests.
Minicomputers provides facility of communication links between multiple
computers .They have word length of 15 bits or more.

The memory varies from 256 kb from 3 Mb.CPU speed ranges from 500
kips to 1 MIPS. Gradually the architectural environments of minicomputer
grow and 32 bit minicomputers called as super mini are introduced.
Minicomputers are used to control machines in manufacturing unit.

The increasing power of microcomputer workstations has made it harder
to distinguish between mini and micro computers. One of the popular mini
computers is the VAX made by Digital Equipment Corporation.


computer is more powerful than

computer has word length of 32 bits or
more. Memory size ranges from 1 MB to more than 16
MB. The CPU speed is in the range of 1
10 MIPS.

can support 100 users in timesharing mode; can
have wide variety of languages and operating systems.

are also used as central host computer in
distributed system. Mainframes are mainly used in
insurance companies, banks, government agencies, etc

are huge in size and are huge in size. Some
popular mainframes are MEDHA, SUPERRY, DEC, IEL.


are most powerful computers .They
has extremely high processing speed and very large
size. They are kept in protective rooms with special
cooling system, power protection and other security

They are the fastest calculating devices ever invented.
They can operate at speed measured in nanosecond to
1 million faster than microcomputer.

speed and power make them ideal for handling
large and complex problems.

use multiprocessing and parallel
processing technologies to solve complex problem
faster. Multiple processor and parallel processing
enables complex problem to be divided into smaller
problems that can be assigned to different processor
and processed in parallel.



They are used in scientific
applications such as weather forecasting, oil
explorations, research, Automobile industry,
Aerospace Industry, Structural mechanics etc.

I n India CRAY, XMP
14, used by
Meteorological department is a mainframe
supercomputer system. The supercomputer
develop in India is PARAM

On the basis of purpose

General Purpose Computer

These computers are used to
perform general task .These computers can store different
programs and can be used to execute counter applications.
These computers can be further classified on the basis of there
processing speed and storage capacity.

Specific Purpose Computers

These computers are designed
to perform only 1 specific task .The programs or instructions are
wired into or permanently stored in these machines. These
machines lacks versatility, but perform there single task quickly
and efficiently.

Eg :

Computer installed in American atomic submarines to
store complex navigational problems .