General purpose computer:

This type of computer can do different types of work. But accuracy level is low. Personal computer (pc) is a kind of general purpose computer.

Special purpose computer:

This type of computer used for any particular work. Accuracy level is high and dedicated type of computer.


Super computer.

Analog computer:

This type of computer works with analogous data.

Digital computer:

These types of computer work with digital signal. Digital signal made with Binary digits; ‘0’ and ‘1’. ‘0’ and ‘1’ used for high and low voltage or indicate ON and OFF situation of voltage. Digital signal are like discrete type.

Hybrid computer:

Hybrid computer made with both analog and digital signal. Fast processing power of analog computer and High accuracy level of digital computer can be found in a Hybrid computer.

Super computer:

World’s fastest calculating device is called as super computer. Super computer can process data or instruction in nano second or peco second.

Two things must present in a super computer;

(i) Roll back process from failure to previous stage.

(ii) Parallel processing. [More than one CPU can handle or process multiple data or instruction.]


Y- MP/C 90; developed by Cray Research Inc. can perform 2.1 cr. calculation in 1 second.

Mainframe computer:

Mainframe computer has less power, less processing speed than super computer. It is also cheaper than super computer. Bank, Insurance companies, Railway system use this type of computer. It follows Time sharing method to process data.


IBM S/390.

Mini computer:

Mini computer is smaller and cheaper than mainframe computer or general purpose computer. It is non-portable type, and used for commercial and technical purpose.

For accounting, word processing, database management, CAD, numerical analysis mini computer is used.


Digital Equipment Corporation builds VAX.

Personal computer:

This computer is build for a particular person for a particular work purpose.

For professional application, database management, accounting, word processing, home and education work personal computer (pc) is used.

IBM first brings the PC in market. PC could be of various models like PC, PC-XT, PC-AT etc. Those are made with respect to INTEL 8088, 80286, 80386 and 80486 microprocessors.Properties of PC:

The cabinet contained Power unit, Main memory, Disk drive, Input output device, Monitor, Floppy disk, Hard disk, Keyboard etc.

Work station:

Workstation is costly and it is used by strong machines, scientists and professionals. It can process high amount of data and can run difficult programs. Advanced technology used for display screen of workstation. It supports O.S like UNIX for multitasking.

Processors of work station are more powerful than general PC’s. Some extremely powerful workstations are called as super micros.


Sun, Apollos, Hewlett packard, Next and IBM workstations.

Portable computer:

In today’s world the demand of small and lightweight computer is getting high. Among this type of computer’s, portable computer is popular one.

Mainly there are three types of portable computer,

(a) Laptop and Notebook.


(c)Personal digital assistant.

Laptop and Notebook:

This type of device can run with battery, so it can be easily portable from one place to another place. Laptop is small and lightweight so we can work with it by placing it in our lap. Notebook’s is a device that is smaller than laptop’s.

These types of portable devices use improved Microprocessors, improved Graphics, High storage memory etc.


Sub-Notebook is a kind of device that is useful for those people who is always travelling from one to another place. This type of device has external floppy disc drive.


Toshiba protege.

Hand-held computer:

Hand-held computer are smaller than sub-Notebook and this type of device mainly used for data collection. It can store twelve thousands of records. Hand-held computers are helpful for security purposes.

Pen-based computing:

It is a kind of very small computer. This device made with writing pad and a light pen. User just touch the pen on the writing pad for give any input.

These types of devices are also known as personal digital assistant or PDAS.


Newton of Apple.