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Classification of Computer are done interns of;

  • Classification by generation.
  • Classification by size.
  • Classification by purpose.
  • Classification by type.



First generation computer:

classification of computer

These computers were developed between 1940 and 1956. Their main memory was made up of vacuum tubes and it used punch cards and magnetic tapes for it secondary storage, and occupies too much space. It consumes too much energy and the cost of maintenance was high. In addition to that, it reliability was also very low. They were mostly general computer. Example of first generation computer includes; Electronic Numeric Integrator Automatic computer (ENIAC), Electronic Storage Integrated Computer (EDSAC) and Universal Automatic Computer (UNIVAC-1).

Second generation computer:

classification of computer

The computers were developed within the period of 1956 to 1965.

It was made up of transistors which took the position of a vacuum as the main memory.  A transistor is a small tiny electronically operated switch that can alternate between ‘ON’ and ‘OFF’ many millions of time in one second. It has an improved reliability, reduces cost of maintenance, occupies less space, produces less energy and consumes lesser amount of energy.

Third generation computer:

classification of computer

This generation of computers was developed between the year 1965 and 1971.

It consists of a mother board made up of silicon (silicon chips) use to house integrated circuits (IC). It has a much improved reliability, very high speed, consumes very small amount of energy compared to the predecessors, much more low cost and cost of maintenance and occupies lesser space. In this generation, the computer operates under the multi – programming and multi – processing concept. This application were monitored and coordinated by the memory.

Fourth generation computer:

classification of computers

This are the generation of computers from 1971 till date, they are the modern day computers. They were developed as a result of an improvement on integrated circuit. They are the first electronic computers that used Large Scale Integrated Circuit (LSIC). In this computer, millions of component could be fitted on a small chip. This aspect alone reduces the size and price of the computer while increasing the power, efficiency and reliability.

This single chips was first produced by the Intel corporation and formed the main memory and logic circuits that perform logical operations of the Central processing Unit (CPU) also known as microprocessor. Storage media in this generation of computer is; diskettes, CD – ROM and also witness an improve in input and output devices.

Fifth generation computer (Under development):

classification of computer

The idea of fifth generation computer started from 1991 through the present date and is running to the future in this period, microprocessor with smaller size, faster operating speed, greater processing capabilities and virtually unlimited memory. This memory was embedded in silicon chips.

The computer will be very small in size and will have the tremendous data processing speed and storage capacity.


Microcomputers:  Here we have Micro computers, Mini computers, Mainframe computers and Supper computers.


This are the most common type of computers used in school, laboratories, offices, etc. they can be used by only one person at a time and are generally smallest in size. It comprises of the following;

  1. a)Desktop: this type of minicomputer is design for stationary use and runs on power from an electronic outlet. The system unit is typically separated from the screen. It usually less costly in price and maintenance.
  2. b)Laptop computer (Note book): These are smaller light weight computer design for movement from place to place. It operates on battery or A.C power. It is design with an LCD screen and the screen is incorporated with the system unit. It also has a touchpad in the unit that contains the processor. It cost of maintenance is higher and it is also more expensive.
  3. c)Tablet computer: this is a portable computer device having a touch sensitive screen that can be use as writing or drawing pad. They are operated with a tablet pen and has the ability to convert handwriting to text.
  4. d)Hand held computer:  These includes; a palm, pocket PC and IPad. They can comprise a small keyboard or a touch sensitive screen but exhibit much fewer functions as compared to the others. They are also called personal digital assistant. They can be carried on palm or pocket hence can be used as notepad, calculator, address book and appointment book.
  5. e)Workstation computer: They are similar to desktop computers but are more powerful and are usually connected to a network. They are generally use as server machines to store and share information with other computers on the network.

Minicomputers; it can take the size of a refrigerator. It less expensive and can perform fewer functions compared to Mainframe computer. The can have multiple inputs and outputs devices that permits more than one user to work on the computer at the same time. It can support up to 100 users or more working at the same time. Can be use by small research organization as a network server.

Mainframe computers;

this type of computer is similar to Minicomputers except that it is more powerful and can support many hundred of users at a time. it has several microprocessor. It provides the function of a centralized storage, processing and management of large amount data such as railway and airline preservation system for the government and business departments.

classification of computer

Supper computers:  This is the most powerful type of computers so far. It has many processors and can perform billions of instruction per second. They are used when it concerns a tremendous deal of instruction that can cause delay with the mainframe computer. It use more advance memory such as bubble memory.


In terms of function, we have computers that are design to carry out many different functions. They are called general purpose computer. They are the digital computers and can perform task such as; pay bills, manage inventories etc.

While others are design to carryout one and only one function, they are call special purpose computers. They include; computers design for military purposes.(tracking airplanes and missiles). Here the sets of instruction use to perform task are stored permanently from the time of manufacture.


In terms of type, we have analogue, digital and hybrid computer.

Analogue computers are those that are working on a continuous variable that is from 1 to infinity

A digital computer is that which is working on a random discrete variable that is zeros and ones (binary digits). Any data input into this computer is first transform into zeros and ones. They treat text and graphics numerically.

A hybrid computer is one that performs both analogue and digital functions, hence working on both discrete and continuous data.