Working of a Computer System

In this blog we will discuss about working of a computer system.

Computers work on the basis of a model called IPO model. It stands for INPUT-PROCESS-OUTPUT model.

Computer input is called data and the output obtained after processing it, based on user‟s instructions is called information. Raw facts and figures which can be precessed using arithmetic and logical operations to obtain information are called data.

The processes that can be applied to data are of two types

  • Arithmetic operations – Examples include calculations like addition, subtraction, differentials, square root, etc.
  • Logical operations – Examples include comparison operations like greater than, less than, equal to, opposite, etc.

The corresponding figure for an actual computer looks something like this –

The basic parts of a computer are as follows

Input Unit

Devices like keyboard and mouse that are used to input data and instructions to the computer are called input unit.

Output Unit

Devices like printer and visual display unit that are used to provide information to the user in desired format are called output unit.

Control Unit

As the name suggests, this unit controls all the functions of the computer. All devices or parts of computer interact through the control unit.

Arithmetic Logic Unit

This is the brain of the computer where all arithmetic operations and logical operations take place.


All input data, instructions and data interim to the processes are stored in the memory. Memory is of two types – primary memory and secondary memory. Primary memory resides within the CPU whereas secondary memory is external to it.

Control unit, arithmetic logic unit and memory are together called the central processing unit or CPU.


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