Classification of Digital Computer

Computer can be classified on the basis of its Usage and Size.


1.  Usage-Wise Classification

(a)  Special Purpose Computer1

These are designed for specific class of application. In this type of computer the instruction set is permanently stored in the computer chip. It performs the assigned task quickly and efficiently.

(b) General Purpose Computer

These computer can be used for a large variety of applications and have versatility in use.

2. Size-Wise Classification:

Computer can be classified on the basis of size also. Size wise computers are categorized into

  • Microcomputer
  • Mini computer
  • Mainframe computer
  • Super computer


(a)  Microcomputer2

The most common type of computers are Micro computers, which is portable Personal Computer that fits on top of a desk. It is a small computer, mainly consists of single chip. Average data transfer rate of a Microcomputer is 5 Lac bytes per second. It can hold from 8 to 32 bit word length. Microcomputers can be subdivided into 2 types

  • Home computer
  • Personal computer

Home computer

They are basically meant for hobbies and games rather than professional tasks. They consist of a keyboard integrated with CPU 4th-genin one box and interfaced with ordinary television and multimedia system used for entertainment and training in various computer centers and home. Examples of these computers are APPLE II, IBM PC JUNIOR etc.

computers are APPLE II, IBM PC JUNIOR etc.


Personal computer

These computer are designed for, small business units and office automation. PC’s are use various application areas like

  • Business & professional application.
  • Computer learning
  • Electronic spread sheet
  • Word processing
  • Accounting
  • Telecommunication

(b) Mini Computer

Mini Computer are larger in size than microcomputers and have a very fast processing speed. It consists of a multiple mini-computer-250x250processing units in a single chip. It uses word length of usually 16, 24, 32 or 64 bits. The data transfer rate is about 4 million bytes per second for Mini Computer. They can support up to 15 to 25 terminals simultaneously. Some important Mini Computers are Magnum VAX Mighty Frame.

(c)  Mainframe Computers

These are very large machines with the capability of parallel processing. The data transfer rate of this machine is 8 million bytes/ second. It uses the word length of usually 24, 32, 48 and 64 or 128 bits. Mainframe is used for centralized data processing like Train Reservation System, Airline Reservation, Mainframe computers can Support over 500 terminals. Some important Mainframe computers are FDM – 3090, VAX 8842 and UNIVAC.

(d) Super Computer

Super computers are much faster and more powerful than Mainframe computers. Their processing speed lies in the range of super400 MIPS, word length 64-96 bit, memory capacity 256 MB and more, hard disk capacity 1000 MB and more, and machine cycle time 4-6 nanosecond(ns). Super-computers are specially designed to maximize the number of FLOPS. Their floating point instructions per second (FLOPS) rating is usually more than 1 gigaflops per second.

Super-computers contains a number of CPU’s which operate in parallel to make it faster. They are used for weather forecasting, weapons research and development, rocketing, in aerodynamics, seismology, atomic, nuclear and plasma physics. Examples of Super-computers are: CRAY 3 (developed by Control Data Corporation), SX-2 (developed by Nippon Electric Corporation, JAPAN), SX-3r etc.

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