Lesson 4.6.4.1

4.6.4.1 Logic gates Quiz: AQA Computer Science, Unit 6

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

In partnership with Revision Ninja

Lesson 4.6.4.1, Logic gates: 20 multiple choice questions for the AQA Computer Science (7517), Unit 6: Fundamentals of computer systems, written with Revision Ninja.

Host it live on the board and students join with a game code on their own devices, or revise alone with Free Play. The answers are revealed in the game.

Host this setFree Play

The 20 questions

  1. What is the output of an AND gate when both inputs are 1?

    • Undefined, because an AND gate needs three inputs
    • The inverse of the input, which is 0
    • 0
    • 1

  2. Which gate outputs 1 only when its inputs differ?

    • XOR
    • NAND
    • AND
    • NOR

  3. What is the output of a NAND gate with inputs A = 1 and B = 1?

    • It is the same as an OR gate's output for these inputs
    • 1
    • 0
    • It cannot be determined without a clock signal

  4. Which gate's output is the inverse of an OR gate's output?

    • AND
    • XOR
    • NOR
    • NOT applied to A only

  5. For an OR gate with inputs A = 0 and B = 1, what is the output?

    • Equal to the value of A, which is 0
    • 0
    • Undefined until a clock pulse arrives at the gate
    • 1

  6. A NOT gate receives the input 0. What is its output?

    • The inverse of an AND gate with no inputs
    • Undefined, because a NOT gate needs two inputs
    • 1
    • 0

  7. Which Boolean expression is equivalent to the output of a two-input NAND gate with inputs A and B?

    • A XOR B
    • A OR B
    • NOT A AND NOT B
    • NOT(A AND B)

  8. A circuit computes Q = (A AND B) OR C. What is the value of Q when A = 1, B = 0, C = 1?

    • 0
    • Undefined, since the AND output and C conflict
    • 1
    • Equal to A XOR C, which is 0

  9. A circuit computes Q = NOT(A OR B). Which input combination gives Q = 1?

    • A = 1, B = 1
    • A = 0, B = 0
    • A = 0, B = 1
    • A = 1, B = 0

  10. Which of the following is the Boolean expression for a half-adder's sum output?

    • A OR B
    • A XOR B
    • NOT(A AND B)
    • A AND B

  11. Which Boolean expression describes the carry output of a half-adder?

    • A AND B
    • A OR B
    • NOT A AND B
    • A XOR B

  12. A half-adder has inputs A = 1 and B = 1. What are its sum and carry outputs?

    • Sum 1, carry 0
    • Sum 1, carry 1
    • Sum 0, carry 1
    • Sum 0, carry 0

  13. A full-adder adds inputs A, B and a carry-in C. Which expression gives its sum output?

    • A OR B OR C
    • A AND B AND C
    • A XOR B XOR C
    • (A AND B) OR C

  14. A full-adder has A = 1, B = 1 and carry-in C = 1. What are its sum and carry-out values?

    • Sum 0, carry-out 1
    • Sum 1, carry-out 1
    • Sum 1, carry-out 0
    • Sum 0, carry-out 0

  15. Which gate combination is typically used to build the carry output of a full-adder from its inputs A, B and C?

    • A single XOR gate with all three inputs, since XOR alone gives the full carry output
    • A NOT gate on each input, because inverting the inputs gives the carry output directly
    • NAND gates only, because NAND cannot be used to build any other gate type
    • AND gates and an OR gate combining the carry from A and B with the carry-in C

  16. A truth table has four rows for two inputs. For which gate is the output 1 only in the row where both inputs are 0?

    • NOR
    • AND
    • XOR
    • NAND

  17. Which statement about D-type flip-flops, as described in the specification, is correct?

    • A D-type flip-flop stores a whole byte at once and cannot hold a single bit of data
    • A D-type flip-flop is a combinational gate whose output depends only on its current inputs
    • An edge-triggered D-type flip-flop can be used as a memory unit that stores a single bit
    • A D-type flip-flop stores its value in a register that is erased whenever the clock rises

  18. A circuit's output is given by Q = NOT(A) AND B. Which input values produce Q = 1?

    • A = 1, B = 0
    • A = 0, B = 0
    • A = 0, B = 1
    • A = 1, B = 1

  19. What is the output of an XOR gate when both inputs are 1?

    • The inverse of an AND gate's output, which is 1
    • 0
    • 1
    • It cannot be determined without a clock signal to the gate

  20. A circuit gives Q = A XOR B with A = 1 and B = 0. What is Q?

    • Equal to A AND B, which is 0
    • 0
    • Undefined until both inputs are set to 1
    • 1

All AQA Computer Science quizzes