Lesson 4.7.3.1

4.7.3.1 The processor and its components Quiz: AQA Computer Science, Unit 7

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 4.7.3.1, The processor and its components: 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. Which component of the processor performs arithmetic and logical operations on data?

    • The program counter, which holds the address of the next instruction
    • The memory address register, which holds the address of the next data item
    • The clock, which generates pulses that synchronise the processor
    • The arithmetic logic unit (ALU)

  2. What is the role of the control unit?

    • It stores data while a program is waiting for input from a keyboard or mouse
    • It holds the value of the program counter so that it does not change during a fetch
    • It performs all the additions and comparisons on the data values in the registers
    • It co-ordinates fetch, decode and execute by sending control signals to other parts of the processor

  3. A processor's clock runs at 3 GHz. How many clock cycles occur each second?

    • 3 x 10^6
    • 3 x 10^9
    • 300
    • 3 x 10^12

  4. Which register holds the address of the next instruction to be fetched?

    • The status register
    • The current instruction register
    • The program counter
    • The memory address register

  5. Which register holds the instruction that is currently being decoded and executed?

    • The memory buffer register
    • The program counter
    • The current instruction register
    • The general-purpose register R0

  6. Which register holds the address of the memory location to be accessed?

    • The memory address register
    • The status register
    • The program counter
    • The memory buffer register

  7. Which register holds data that has just been read from memory, or is about to be written to it?

    • The current instruction register
    • The memory buffer register
    • The memory address register
    • The program counter

  8. What is the main purpose of the status register?

    • It stores the clock frequency so that the processor can monitor its own speed
    • It holds the address of the next instruction to be fetched from memory
    • It holds flags that record conditions such as whether the last result was zero or negative
    • It holds the data currently being sent to the output device, such as a monitor

  9. What are general-purpose registers used for?

    • Controlling the speed of the system clock as the program runs
    • Temporarily holding data and intermediate results during processing
    • Holding the address of every memory location in the computer
    • Permanently storing programs so that they survive a power cut

  10. A processor's program counter holds 0x0200. The instruction at that address is 2 bytes long, with byte addressing, and there is no branch. What does the PC hold after the fetch?

    • 0x0200
    • 0x0201
    • 0x0202
    • 0x0400

  11. A clock runs at 2.5 GHz and a task needs 5 x 10^9 clock cycles. How long does the task take?

    • 2 seconds
    • 5 seconds
    • 0.5 seconds
    • 20 seconds

  12. Which pair of registers is used together during a memory read?

    • A general-purpose register and the ALU, which together hold the working values during an arithmetic operation
    • The current instruction register and the clock, which together hold the instruction and the timing of its execution
    • The memory address register and the memory buffer register
    • The program counter and the status register, which together record the next instruction and the flags for the last result

  13. Why does the processor need a memory address register separate from the program counter?

    • The PC holds the address of the next instruction, whereas the MAR holds the address used for any memory access, including data
    • The MAR stores the status flags for each result, while the PC stores the speed of the clock in cycles per second
    • The MAR holds the instruction currently being executed, while the PC holds the result of the last calculation performed
    • The PC and the MAR are the same register in every processor design, and only the name differs between manufacturers' products

  14. Which component decodes the instruction held in the current instruction register?

    • The arithmetic logic unit
    • The memory buffer register
    • The clock
    • The control unit

  15. Which combination of components is most directly involved in adding two numbers held in registers?

    • The program counter and the MAR only, with no data path
    • The MBR and the CIR alone, without the ALU
    • The ALU, using values held in general-purpose registers
    • The clock and the status register alone, without any other components

  16. What does a carry flag in the status register indicate?

    • The last arithmetic operation produced a result that did not fit in the register
    • The processor has received an interrupt request from a device
    • The memory address supplied to the MAR is not valid for this computer
    • The program counter has reached the last location of main memory

  17. Which component is responsible for controlling the timing of the processor's operations?

    • The status register
    • The memory buffer register
    • The clock
    • The ALU

  18. A processor runs at 1 GHz and each instruction takes 4 clock cycles. How many instructions can it execute per second?

    • 4 x 10^9
    • 2.5 x 10^8
    • 2.5 x 10^9
    • 1 x 10^9

  19. During an instruction fetch, the PC holds 300. Which sequence of register transfers is correct?

    • MAR gets 300, memory returns the instruction into the MBR, the MBR is copied to the CIR, and the PC increments
    • PC gets 300, memory returns the instruction into the CIR, the MBR is copied to the MAR, and the ALU increments the MBR
    • CIR gets 300, memory returns the instruction into the PC, the MAR is copied to the MBR, and the PC then decodes the instruction
    • MBR gets 300, memory returns the address into the MAR, the CIR is copied to the PC, and then the ALU increments the CIR

  20. Which of these is part of the processor rather than main memory?

    • The random access memory module that holds the running program
    • The set of general-purpose registers
    • The memory chips that hold the data for the display
    • The hard disk controller that reads files from the drive

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