OCR Computer science J277 component 1

1) What is a computer?

2) How does a computer do its function and through what cycle.

An electronic device which takes input, processes it and executes an output.

A computer does it function through the CPU which FETCHES instructions, DECODES them and EXECUTES them ( Fetch, Decode, Execute Cycle

What is the CPU?

The CPU stands for Central Processing Unit and it is the brain of the computer. This is where the FDE cycle happens.

What is the CPU made up of?

The CPU is made up of:

CU - Control Unit

ALU - Arithmetic Logic Unit

Cache

Registers

What happens in the 1st stage of the F-D-E cycle / Fetch stage?

In the first stage of the F-D-E cycle, the CPU FETCHES the next data and instructions from main memory (RAM).

Then, the instructions will be brought back into the CPU

What happens in the 2nd stage of the F-D-E cycle / Decode stage?

In the Decode stage, the CPU will inspect the instructions and DECODE / WORK OUT what need to be done

What happens in the last stage of the F-D-E cycle / EXECUTE stage?

The CPU EXECUTES / CARRY OUT the instructions which could be :

• Getting more data and instructions from main memory (RAM)

• Performing a calculation

• Storing information into main memory / RAM

What does the control unit do?

The Control Unit

• sends SIGNALS to CONTROL how DATA MOVES around the CPU

• Co - ordinates the CPU’s operations

• can be thought of like being the CPU’s nervous system