The CPU and the fetch-execute cycleWhat is the purpose of the CPU?

The purpose of theCPUis to processdata. The CPU is where processes such as calculating, sorting and searching take place. Whatever is done on our computers, such as checking emails, playing games and doing homework, the CPU has processed the data we use.

The CPU is made up of three main components, the control unit, the immediate access store and the arithmetic and logic unit.

The control unit

The control unit controls the flow of data within the system.

The control unit controls and monitors communications between the hardware attached to the computer. It controls the input and output of data, checks that signals have been delivered successfully, and makes sure that data goes to the correct place at the correct time.

Immediate access store

The immediate access store is where the CPU holds all the data and programs that it is currently using. You can think of it like the numbers typed into a calculator – they are being stored inside the calculator while it processes the calculations. The immediate access store is often referred to as the registers in the CPU.

Arithmetic and logic unit

The arithmetic and logic unit (ALU) is where the CPU performs the arithmetic and logic operations. Every task that your computer carries out is completed here. Even typing into a word processor involves adding binary digits to the file, and then calculating which pixels on the screen should change so that you can see the characters. The ALU’s operations fall into two parts:

• the arithmetic part, which deals with calculations, eg 1 + 2 = 3
• the logic part, which deals with any logical comparisons, eg 2>1