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Function of a Computer

Functioning of a computer is similar to the life of a human. For example, let us understand with the following illustration.
  • Consider that your mathematics teacher has given you home work to perform addition of two numbers, and to submit it on the next day.
  • The diagram below performs three actions:
    • Getting the data
    • Performing an action
    • Publishing the result

  • The above metrics is maintained in the computer system also.
  • Here we call the processes as
    • Input
    • Processing
    • Output
  • These procedures are in turn named as Input-Process-Output Cycle (I-O-P Cycle).
Note: Data are viewed as a lowest level of abstraction from which knowledge and information are derived.

Basic Functional Components of a Computer

The various functional units of a computer system together constitute the organization of the computer. Basically a computer consists of three major units namely:
  • Input Unit
  • Central Processing Unit (CPU)
  • Output Unit

Basic Structure of a Computer

Let us learn each section of the computer in detail

Input Unit
  • It comprises of various input devices, which help to input program, data, information and various operating commands into the computer.
  • The main function of input unit is to read the information contained in the program and to transfer that information to the CPU.
  • The information received is converted into binary digits and stored in the computer memory
  • Input devices are used to give input.
  • Various input devices are
    • Keyboard
    • Mouse
    • Joystick
    • scanners
    • Magnetic Ink Character Reader (MICR)
Note: Input device is that any machine that feeds data into a computer.

Central Processing Unit

  • Central Processing Unit (CPU) forms the heart of a computer system.
  • CPU is the control centre for a computer.
  • Memory unit, Arithmetic Logic Unit (ALU) and control unit together constitutes CPU.
  • As soon as the program is fed into the input unit, the control unit gives necessary signals to the memory unit. Then the relevant data is sent to Arithmetic Unit.
  • The various units are discussed below
    • Arithmetic Logic Unit: Performs all types of operations such as addition, subtraction, multiplication and division as well as logical comparison.
    • Memory Unit: It is the main part of the computer where the program, data, instruction, certain software and results were stored. They can be retrieved at any time whenever required.
    • Control Unit: The control unit controls the operation of all the other units of a computer. It has a direct control over the input and output units.
Note: Memory Unit is otherwise called as storage unit, primary memory.

Output Unit

  • The results of computations from the memory unit were taken to the output unit and the results were shown in a human understandable language.
  • Output device helps to give results to the outside user of the computer system.
  • Output devices such as
    • Monitor
    • Printer
    • Card Punch
    • Plotter
    • Speech synthesizer
    • Projectors
Note: Computer is aware of only two data such as 0 and 1 called Binary Digits

Four main components of a computer

Systems to be executed properly, then the following components are essential. They are
  • Hardware
  • Software
  • Operating System
  • User

Basic components of a computer


  • Hardware is the physical parts of a computer.
  • As it is distinguished from the data it contains or operates on, and the software that provides instructions for the hardware to use it.
  • It can be touched and seen.
  • All the input and output devices compromises a hardware
  • Example - Monitor, Keyboard, mouse, printer and other peripherals.


  • Set of instruction used to execute or to operate a computer.
  • Instructions are given in the form of bits and bytes.
  • Software is divided into 3 major categories.
  • They are
    • System Software - It helps in running the computer hardware and computer system. It includes
      • Device driver
      • Server
      • Utilities
      • Windows System.
    • Application Software - It allows the end user to accomplish one or more specific task. It includes
      • Air ticket booking
      • Net Banking
      • Online shopping
      • Computer Games
    • Programming Software / Language Processors - It is used to assist the programmer in writing computer programs and software using different programming languages. It includes
      • Complier
      • Debugger
      • Linkers
      • Interpreters

Operating System

  • An operating system is a program which acts as an interface between a user and the hardware.
  • It controls all the components of the computer system.
  • Various operating systems are
    • Windows 95/98/2000
    • Windows XP
    • Unix
    • Linux
    • Windows Vista


  • Person who uses a computer or an internet service.
  • Users are of two types, namely
    • Single user
    • Multi user

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