Instructions

The CPU of a computer carries out instructions supplied by a computer program.

Have a look at this simulation to remind yourself of the fetch-decode-execute cycle you studied in episodes 7 and 8.

Every processor or processor family has its own unique instructions that it can understand.

These instructions make up the instruction set of the microprocessor.

The instructions are called machine language instructions and are in binary format - strings of 1s and 0s - the only ‘language’ that the microprocessor can understand.

The CPU decodes these bit patterns into the actions that it has to perform and what it has to perform them on.

Control unit

Register

Address 1

Click the Start button to watch the cycle. You can pause, resume and re-run the simulation.

Address 2

Data

CPU

Start

Bus

Address

Decoder

Pause

ALU

Proceed

ME M O R Y

Program counter

Instruction

Registers

The fetch - decode - execute cycle