Lesson 4.7.3.2

4.7.3.2 The fetch-execute cycle and registers Quiz: AQA Computer Science, Unit 7

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 4.7.3.2, The fetch-execute cycle and registers: 20 multiple choice questions for the AQA Computer Science (7517), Unit 7: Fundamentals of computer organisation and architecture, written with Revision Ninja.

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The 20 questions

  1. What are the three sequential stages of the processor cycle?

    • Read, write, clear
    • Input, process, output
    • Load, store, branch
    • Fetch, decode, execute

  2. Which register is loaded with the memory address of the next instruction to be fetched?

    • Memory address register
    • Memory buffer register
    • Current instruction register
    • Status register

  3. Which register temporarily holds data read from or written to memory?

    • Memory Data Register
    • Current Instruction Register
    • Program Counter
    • Memory Address Register

  4. Which processor component decodes the opcode stored in the Current Instruction Register?

    • Status register
    • Arithmetic logic unit
    • Clock
    • Control unit

  5. Which component carries out arithmetic calculations during the execute stage?

    • CIR
    • ALU
    • MAR
    • PC

  6. A processor takes 3 clock cycles to fetch, 1 to decode and 2 to execute an instruction. How many cycles does each instruction take?

    • 6
    • 5
    • 3
    • 9

  7. A program has 1,000 instructions, each taking 6 clock cycles, on a 2 MHz clock. How long does the program take to run?

    • 0.3 ms
    • 30 ms
    • 3 s
    • 3 ms

  8. Which register holds the instruction while it is being decoded by the control unit?

    • MAR
    • PC
    • Status register
    • CIR

  9. What is the primary role of the memory buffer register during a fetch stage?

    • Stores jump addresses
    • Holds fetched data
    • Calculates arithmetic
    • Decodes opcodes

  10. What condition causes the continuous fetch-execute cycle to stop operating?

    • Halt instruction
    • Register overflow
    • Branch taken
    • Clock tick

  11. Which specialised register automatically increments during every fetch stage?

    • Status Register
    • Program Counter
    • Accumulator
    • Memory Address Register

  12. The PC contains 1500 and the instruction is 2 bytes long with byte addressing. After the fetch, and before executing a non-branch instruction, what does the PC contain?

    • 1501
    • 1500
    • 1600
    • 1502

  13. How does execution proceed when a conditional branch instruction condition evaluates to false?

    • Restarts completely
    • Sequentially
    • Halts immediately
    • Branches backwards

  14. Which component checks the zero flag condition during a conditional branch?

    • Control unit
    • Arithmetic logic unit
    • Memory buffer register
    • System clock

  15. What main action occurs during the fetch stage of the fetch-execute cycle?

    • Retrieving an instruction
    • Decoding an opcode
    • Executing an operation
    • Writing to RAM

  16. Which internal CPU bus transfers the contents of the PC to main memory?

    • Address bus
    • Data bus
    • Control bus
    • Internal bus

  17. Which of these is NOT one of the three stages of the fetch-execute cycle?

    • Decode
    • Fetch
    • Execute
    • Store

  18. Why is an instruction copied from the MBR to the CIR during fetch?

    • Updates status flags
    • Increments the PC
    • Frees the MBR
    • Clears the MAR

  19. Where is the result of an arithmetic operation usually written during the execute phase?

    • To the CIR
    • To the MAR
    • To main memory
    • To a register

  20. A processor runs at 4 GHz, and each instruction takes an average of 8 clock cycles. How many instructions does it execute per second?

    • 3.2 x 10^10
    • 4 x 10^9
    • 5 x 10^8
    • 5 x 10^6

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