Base on physical size performance and application areas. The computers are equally classify in four major categories:

• Supers computers
• Maine frame
• Micro computer
• Mini

1.Micro computers

It is a small, low cost digital computer which usually consists of a micro process, a storage unit, and input and output channel, all of which may be on one chip center on to one. The addition of the power supply and collecting cables appropriate peripherals (keyboard, monitors, printer, disk drive and others), and operating system and other software program can provide a complete micro computer system (desktop, lap tops, etc).

2.Mini computer

This is a small digital computer which normally is able to process and store less data than a mainframe but more than a micro computer while doing so, less happily than a mainframe but more happily than a micro computer.

3.Mainframe

It is a neutral high performance computer made for high volume intensive computing. It consists of a high end computer process with relative peripherals diverse, capable of supporting large volume of data processing, high performance online transaction processing and extensive data storage delivered mainframe at the second larger computer families.

5.Super computer

There are special purpose machine which are specially designed to maximize the flops, there are the largest in the computer family, it has the highest processing speech at a given time for solving scientific and engineering problem.