GCSE J277 - How the CPU Works Keyword Quiz

Holds the memory address of the next instruction to be executed

Stores intermediate results of calculations in the ALU

Holds an memory address about to be used by the CPU. This could point to data or an instruction

Holds the actual data or instruction, either fetched from memory or waiting to be written to memory

Load data from memory

• Fetch

• Decode

• Execute

Memory address copied from the program counter to the MAR

• Fetch

• Decode

• Execute

Instruction copied from memory to the MDR

• Fetch

• Decode

• Execute

Write data to memory

• Fetch

• Decode

• Execute

Control unit works out what the instruction in the MDR needs to do

• Fetch

• Decode

• Execute

Perform a calculation or logic operation

• Fetch

• Decode

• Execute