Computer CPU (Central Processing Unit) - Computer Fundamentals

What is CPU? How does it work?

Central Processing Unit (CPU) consists of the following features −

  • CPU is considered as the heart of the computer.
  • CPU helps in performing all types of data processing operations.
  • CPU stores data, intermediate results, and give instructions (program).
  • It controls the operation of all parts of the computer.


CPU itself has following three components.

  • Memory or Storage Unit
  • Control Unit
  • ALU(Arithmetic Logic Unit)


Memory or Storage Unit

This unit stores instructions, data, and intermediate results which are taken as input from the user for later use. It is also called as internal storage unit or main memory or the primary storage or Random Access Memory (RAM). This unit provides information to other parts of the computer as and when it required.

Its size affects speed, power, and capability. There are two types of memories i.e Primary memory and secondary memory. Functions of the memory unit are −

  • It stores all the data and the instructions required for processing to execute the programs.
  • It stores intermediate results of processing.
  • It stores the final results that need to be processed before these results are released to an output device.
  • All inputs and outputs are transmitted through the main memory.

Control Unit

This unit controls the operations of all parts of the computer but does not take part in actual data processing operations.

Functions of this unit are −

  • It is helps in controlling the transfer of data and instructions among other units of a computer.
  • It manages , controls and coordinates all the units of the computer.
  • It receives the instructions from the memory, interprets them, and directs the operation performed by the computer.
  • It communicates with Input/Output devices for transfer of data or results from storage.
  • It does not process or store data.

ALU (Arithmetic Logic Unit)

This unit consists of two subsections namely,

  • Arithmetic Section
  • Logic Section

Arithmetic Section

Computer performs operations to execute the programs required by the user. It contains arithmetic operations like addition, subtraction, multiplication, and division for calculations. These arithmetic operations can be used repeatedly to perform specific programs. All complex to simple operations can be done easily by using repeatedly the above operations.

Logic Section

This section deals with the logical operations such as comparing, selecting, matching, and merging of data.

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