CPU Fetch-Decode-Execute Cycle

A CPU (central processing unit) executes and manages the rest of the hardware inside a computer system - it is the brain of a computer!

The CPU is made up of the main memory, the processor and the cache memory.

It's job is to process data (by processing we mean searching, sorting, calculating and decision making).



The CPU follows the Fetch-Decode-Execute cycle.


  • The Fetch Stage: the CPU use a piece of hardware called the 'address bus', this is where the CPU asks the RAM for some data. The RAM then responds with this data on the 'Data Bus'. 


  • The Decode Stage: This is where the CPU converts the instructions in to a way in which it understands it. It then gets things ready for the next step. 

  • The Execute Stage: This is where data processing happens. Instructions are carried out on the data, as soon as the command is completed it starts the next one. 


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