2. The computers have been
classified into three categories:-
1.Digital computer 3.Hybrid computer2.Analog
computer

3. Digital computer
The digital computers work upon discontinuous
data .They convert data into digits and all
operations are carried out on these digits at
extremely fast rates. A digital computer
basically knows how to count the digits. Digital
computer are much faster than analog
computers and far more accurate. Computers
are used for business and scientific
applications are digital computer.

4. Purpose wise Digital computers
• They can be classified into two:-
General
purpose
Special
purpose

5. Digital Computers
SpecialPurpose
This is the one that is
designed to perform
a specific task. The
instructions to carry
out the task m are
permanently stored
in the machine. For
the specific tasks,
this type of computer
works efficiently but
such computer are
not versatile.
GeneralPurpose
This is the one that c
an work on different
types of program
inputs to it and thus
be used in countless
applications. The
program are not
permanently stored
but are input at the
time of execution.
These computers are
very versatile.

6. Size and performance wise
They can classified into:-
1.Embedded 2.Micro
3.Mini 4.Mainframes
5.Super

7. 1.Embedded computers
Computer exist in a wide range of sizes and
power. The smallest are embedded within the
circuitry of appliances, such as television,
washing machine and wrist watches. These
computers are typically programmed for a
specific task, such as turning to a particular
television frequency or keeping accurate time.

8. 2.Micro computer
It is computer whose CPU is a microprocessor. A
microprocessor is a processor whose all
component are on a single integrated-chip. Those
are normally single-processor, single user systems
designed for performing basic operation like
educational,training,small business applications,
playing games etc. These are mainly used in
offices,homes,schools,shops,stores etc.IBM
PCs,Apple mac,IBM PS2 are some popular
computers of this range.

9. Three main categories of
Microcomputer are:-
Programmable
Computer or
PDAs
Laptop
Computers
and PCs
Workstations

10. Programmable computer or PDAs
It vary enormously in their computational
power , speed, memory , and physical size.
The smallest of these computers can be held
in one hand and are called personal digital
assistants(PDAs).they are used as notepads,
scheduling systems, and address ;if equipped
with a cellular phone, they can connect to
worldwide computer networks to exchange
information regardless of location.

11. Laptop computer and desktop
personal computer
They are typically used in business and at homes to
communicate on computer networks, for word
processing to track finances, and to play games. They
have large amounts of internal memory to store
hundreds of programs and documents. They are
equipped with a keyboard; a mouse, a track ball or
other pointing devices ;and a video display monitor or
liquid crystal display or other pointing devices; and a
video display monitor or liquid crystal display to display
information. Laptop computer can be carried out in
brief cases. Laptop computers are so called as they can
sit on a lap and desktop computers are so called as
they can sit on a desk.

12. Workstations
They are similar to personal computers but have
a greater memory and more extensive
mathematical ablities,and they are connected
to other workstations or personal computers
to exchange data. They are typically found in
scientific, industrial and business
environments that require high levels of
computational abilities.

13. 3.Mini computers
These are also called mid range servers, are more
powerful computers than micro computers in
terms of processing power and capablities.They
are mainly multiuser systems where many users
simultaneously work on the systems. They posses
greater storage capacity and larger memories as
compared to microcomputers. These are even
capable of handling more input-output devices.
Examples:-PDP-11,VAX,7500 MAGNUM etc.
By ASHISH NAGPAL

14. 4.Mainframe computer
They are designed to handle huge volumes of data and
information. These can support more than hundred
users at same time. These very large and expensive
computers having great processing speeds and very
large storage capacity and memory as compared to
minicomputers. These computers even possess and
work with more than processor at the same time. Thus
one can say these are multiuser,multiprocessir systems.
For mainframe computers very sophisticated operating
systems are needed to control and superwise their
operation.
Examples:-ICL 39,CDC 6600,VAX 8842,IBM
3090/600,IBM4381
By ASHISH NAGPAL

15. 5. Super computer
They are most powerful computers among digital computers. These
consist of several processors running together thereby making
them immensely faster and powerful. These computers are
capable of handling huge amounts of calculations that are
beyonds human capablities.super computer can perform billions
of instruction per second. Some of the today’s super computers
have the computing capability equal top that of 40000 micro
computers. A Japanese super computer has calculated the value
of Pi(λ) to 16 million decimal places. These computers cost in 15-
20 million dollar range. These are mainly used in application like
weather forecasting, nuclear science research. Aerodynamics
modelling,siesmology,metrology etc.
Examples:-CRAY X-MP-14,CDC-205,ETA GF-10,FUJITSU VP-400,NEC
SX-2,PARAM,PACE
By ASHISH NAGPAL

16. Difference between
Main-Frame Computers
• They are designed to handle
huge volumes of data and
information.
• These can support more
than hundred users at same
time. These very large and
expensive computers having
great processing speeds and
very large storage capacity
and memory as compared
to minicomputers.
Super Computers
• They are most powerful
computers among digital
computers
• . These computers are
capable of handling huge
amounts of calculations that
are beyond human
capabilities .
By ASHISH NAGPAL

17. Analog Computers
• Continuous quantities are used
• Computations (calculations of mathematics &
physics) are carried out with physical quantities
such as voltage , length , temperature etc.
• Devices that measure theses quantities are
analog devices e.g. voltmeter , ammeter etc.
• Main advantage – calculation takes parallel
• They are poor in accuracy
By ASHISH NAGPAL

18. Hybrid Computers
• It utilized the best qualities of both the digital and
analog computers
• In these computers some calculations take place in
analog manner and rest in digital .
• Mainly used in hospitals for measuring heart beat
of patient , blood pressure etc. and also for
weather forecasting
• Analog and hybrid computers perform special tasks
By ASHISH NAGPAL