PC and ACC in the FDE Cycle

Part of Program Counter & Accumulator · Section 5 of 8

DiagramUnit: 3.4 Computer SystemsGCSE

This diagram covers PC and ACC in the FDE Cycle within Program Counter & Accumulator for GCSE Computer Science. Revise Program Counter & Accumulator in 3.4 Computer Systems for GCSE Computer Science with 15 exam-style questions and 12 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 5 of 8 in this topic. Focus on the labels, the relationships between parts, and the explanation that turns the diagram into an exam-ready answer.

PC and ACC in the FDE Cycle

FDE Cycle: When PC and ACC Change FETCH PC → MAR Get instruction PC = PC + 1 (PC increments) DECODE Control Unit interprets instruction (no PC/ACC change) EXECUTE ALU performs calculation Result → ACC (ACC updated) Example: ADD 5 (add 5 to ACC) Step 1: FETCH • PC = 100 (address of ADD instruction) • PC → MAR, fetch instruction • PC increments: PC = 101 Step 2: DECODE • CU: "This is an ADD operation" • Prepare ALU, no register changes Step 3: EXECUTE • ACC = 8 (current value) • ALU: 8 + 5 = 13 • ACC = 13 (result stored)

Practice questions for Program Counter & Accumulator

What does the Program Counter (PC) store?

  • A. The result of the last arithmetic operation
  • B. The address of the next instruction to be fetched
  • C. The current instruction being decoded
  • D. The data retrieved from memory
1 markfoundation

Explain what happens to the Program Counter during the fetch stage of the FDE cycle.

2 marksstandard

Quick recall flashcards

What does PC stand for?
Program Counter
What does ACC stand for?
Accumulator

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Comparison: PC vs ACC

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