What is the function of CPU in a computer system ? What are its subunits ?

The CPU or the Central Processing Unit is the main control centre and processing unit. It is also called brain of the computer as it guides, directs, controls and governs the performance of a computer.

The CPU has three sub-components which are as follows:

1. Arithmetic and Logic Unit (ALU) — It is responsible for carrying out the arithmetic instructions (add, subtract, multiply, divide) and making logic decisions (greater than, less than, equal to).
2. Control Unit — It is responsible for controlling and supervising the processing.
3. Registers — The CPU uses these small units of data holding places to temporarily hold some important processing-information during the time the processing is taking place.