Fetch–Decode–Execute Cycle

The fetch–decode–execute cycle is the basic activity of a CPU. It describes how the CPU retrieves an instruction (copies it from main memory into a register,) understands what to do with it, and then carries out (= executes) the instruction.

In each cycle, the CPU processes one instruction by going through these 3 main stages: fetch, decode, and execute.

This cycle allows a computer to perform complex tasks by breaking down instructions into smaller, manageable steps.

This approach to processing instructions is foundational for all modern computing, enabling rapid and continuous task execution.

On the next slides, we'll examine each stage in detail to understand how the CPU completes an instruction.