1. Classification of computers
Computers come in many sizes and capabilities. Based on the hardware, utility, size and capacity computers are classified.

2. A) Based on size & Capacity 1. Micro Computer
Because of its small size and use of microprocessor, this computer is called Micro Computer.
It is low-cost and the word length of microcomputer lies in the range of 8 to 32 bits.
Ex: IBM PC’S, Apple Mac,
IBM PS/2.

3. Advantages: Disadvantages:
Small and portable
Relatively inexpensive.
Consume less space & power
Relatively slow
Its storage capacity is less.

4. 2. Mini Computers
Mini computers are larger than micro computers and are more powerful in terms of processing power.
These are mainly multiprocessor system where many users simultaneously work on the systems.
It possess greater storage capacity and larger memories as compared to microcomputer.
EX: PDP 11, IBM (8000), VAX7500

5. Advantages: Disadvantages:
It is a general purpose computer.
Its storage capacity is about 2 mega words.
It can support more terminals.
It is relatively inexpensive.
They are slower when compared with main frame computers.
Memory is less than mainframes.

6. 3. Mainframe Computers
These computers are larger, faster and more expensive than other general purpose computers.
These are used to handle huge volumes of data.
For mainframe computer, highly sophisticated OS are needed to control and supervise their operations.
They are used where large amount of data are to be processed or very complex calculations are to be made.
It is used in research organizations, large industries, business and government organizations where large database is required.
Ex: IBM’s ES000, VAX 8000 and CDC 6600.

7. Advantages They are capable of handling all tasks.
They require large room space.
Consumption of electricity is very
high.
Maintenance cost is also very high.

8. 4. Super Computers It is the most powerful of all computers.
They have a high processing speed.
It is specially designed to maximize the number of FLOPS [Floating Point Operations Per Second].
This can perform billions of instructions per seconds.
Whether forecasting, space research, weapons research, Atomic research are some of the applications.
Ex: CRAY-3, Cyber 205 and PARAM

9. Advantages: They use several processors working simultaneously.
They process at a rapid speed.
They have more main memory.
They have operations done in
parallel, rather than sequentially.

10. B) Based on mode of use 1.Desktop computer
It also known as personal computer (PC).
Intended for standalone use by an individual.
Consist of a system unit, a display monitor, a keyboard, internal hard disk storage and other peripheral devices .
Computer manufactures are APPLE, IBM, Dell and Hewlett - Packard.

11. 2. Laptop It is a portable computer is also known as “notebooks”.
Small computers which enclose all the basic features of a normal desktop computer.
It can be used anywhere and at anytime.
Computers do not need any external power supply as rechargeable battery.
Expensive as compared to
desktop.

12. 3. Hand-held Computers
It also called personal digital assistant (PDA).
It can be stored in a pocket and used while the user is holding it.
The palmtop computers accept handwritten inputs using an electronic pen, which can be used to write on a palmtop’s screen.
These have small disk storage and can be connected to a wireless network.
This has also facilities to be used as a mobile phone, Fax and machine.
Ex: Apple Newton, Casio Cassiopeia and Franklin e Bookman.