CLASSIFICATION OF COMPUTERS ACCORDING TO SIZE,TECHNOLOGY AND PURPOSE

According to size
• Supercomputers
• Mainframe Computers
• Minicomputers
• Workstations
• Microcomputers, or Personal Computers

Supercomputers :
are widely used in scientific applications such as aerodynamic design simulation, processing of geological data.

• Supercomputers are the most powerful computers. They are used for problems requiring complex calculations.
• Because of their size and expense, supercomputers are relatively rare.
• Supercomputers are used by universities, government agencies, and large businesses.

Mainframe Computers: 
are usually slower, less powerful and less expensive than supercomputers. A technique that allows many people at terminals, to access the same computer at one time is called time sharing. Mainframes are used by banks and many business to update inventory etc.
• Mainframe computers can support hundreds or thousands of users, handling massive amounts of input, output, and storage.
• Mainframe computers are used in large organizations where many users need access to shared data and programs.
• Mainframes are also used as e-commerce servers, handling transactions over the Internet.

Minicomputers: 
are smaller than mainframe, general purpose computers, and give computing power without adding the prohibitive expenses associated with larger systems. It is generally easier to use.

• Minicomputers usually have multiple terminals.
• Minicomputers may be used as network servers and Internet servers.

Workstations
• Workstations are powerful single-user computers.
• Workstations are used for tasks that require a great deal of number-crunching power, such as product design and computer animation.
• Workstations are often used as network and Internet servers.


Microcomputers, or Personal Computers :
is the smallest, least expensive of all the computers. Micro computers have smallest memory and less power, are physically smaller and permit fewer peripherals to be attached.

• Microcomputers are more commonly known as personal computers. The term “PC” is applied to IBM-PCs or compatible computers.
• Desktop computers are the most common type of PC.
• Notebook (laptop) computers are used by people who need the power of a desktop system, but also portability.
• Handheld PCs (such as PDAs) lack the power of a desktop or notebook PC, but offer features for users who need limited functions and small size.

Personal Computers(PC):

• Desk Top
• Lap Top
• Palm Top
• PDA

According to Technology

• Analog Computers
• Digital Computers
• Hydride Computers

Analog Computers:
These computers recognize data as a continuous measurement of a physical property ( voltage, pressure, speed and temperature).

Example: Automobile speedometer

Digital Computers:
These are high speed programmable electronic devices that perform mathematical calculations, compare values and store results. They recognize data by counting discrete signal representing either a high or low voltage state of electricity.

Hybrid Computers:
A computer that processes both analog and digital data.

According to Purpose

1. General purpose Computers
2. Special Computers

General purpose Computers
A ‘General Purpose Computer’ is a machine that is capable of carrying out some general data processing under program control.

Refers to computers that follow instructions, thus virtually all computers from micro to mainframe are general purpose. Even computers in toys, games and single-function devices follow instructions in their built-in program.

Special purpose Computers
A computer that is designed to operate on a restricted class of problems.
Use special purpose computer equipment to obtain patient diagnostic information.

reference: http://wasaa.wordpress.com/2008/06/22/classification-of-computers/