Fetch-Execute Cycle | 1.1b | OCR GCSE Computer Science (Registers)

11 flashcards

What is the purpose of the CPU?

To fetch, decode and execute instructions stored in main memory (RAM)

What happens if the Fetch-Execute cycle?

Instructions are fetched from RAM and are transferred to the registers.

Which register in particular stores instructions?

Memory Data Register (MDR)

What happens if the Execute stage of the F-E cycle?

- Instructions are decoded by the control unit (CU) and are then executed. - Any mathematical calculations are performed by the ALU and stored in the Accumulator (ACC).

Program Counter (PC)

Stores the address of the next instruction to be fetched from RAM. - The address from the PC is copied into the Memory Address Register (MAR)

Why is the program counter incremented (increased) by 1?

Because it always shows the address of the next instruction.

Memory Address Register (MAR)

Stores the address of the current instruction to be fetched from RAM, after it has been copied from the PC.

Memory Data Register (MDR)

Stores the instruction fetched from RAM to CPU, identified by the MAR.

Accumulator (ACC)

Stores the results of any executions e.g. calculations made by the ALU.

Data

The actual value or instruction being processed.

Address

The location in memory where data or an instruction is stored.