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Information coding systems: AQA A‑Level Computer Science questions

Every AQA A-Level Computer Science exam question on 4.5.5 Information coding systems, 2020–2025, with its mark scheme and examiner’s report.

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561 questions

  1. Q03.1

    June 2025 · AS Paper 2

    1 mark4.5.5 Information coding systems
    The whole paper ↗
    June 2025 AS Paper 2, question 03.1: The character Q has the binary representation 1010001 in ASCII. What is the binary representation of the character T in ASCII? [1 mark]

  2. Q03.2

    June 2025 · AS Paper 2

    1 mark4.5.5 Information coding systems
    The whole paper ↗
    June 2025 AS Paper 2, question 03.2: Unicode was introduced to overcome some of the limitations of ASCII. State one limitation of ASCII that Unicode overcomes. [1 mark]

  3. Q07.2

    June 2025 · AS Paper 2

    2 marks4.5.5 Information coding systems4.6.4 Logic gates
    The whole paper ↗
    June 2025 AS Paper 2, question 07.2: State the type of parity that is computed by the logic circuit in Figure 3 and give a reason for your answer. [2 marks] Type of parity Reason

  4. Q07.3

    June 2025 · AS Paper 2

    3 marks4.5.5 Information coding systems
    The whole paper ↗
    June 2025 AS Paper 2, question 07.3: Alice wants to send a 4-bit message to Bob but is worried about errors. Alice decides to use a parity bit to allow some error checking. Describe how Alice can s

  5. Q07.4

    June 2025 · AS Paper 2

    1 mark4.5.5 Information coding systems
    The whole paper ↗
    June 2025 AS Paper 2, question 07.4: Describe one limitation of using a parity bit for error detection. [1 mark]

  6. Q10.2

    June 2024 · Paper 2

    2 marks4.7.3 Structure and role of the processor and its components4.5.5 Information coding systems
    The whole paper ↗
    June 2024 Paper 2, question 10.2: The value in memory location 130 before the program is executed is the program’s input and the value stored in memory location 130 when the program finishes exe

  7. Q02.2

    June 2023 · Paper 2

    2 marks4.5.5 Information coding systems
    The whole paper ↗
    June 2023 Paper 2, question 02.2: Explain what the checksum is used for and outline how the checksum’s value will be determined. [2 marks] Explain what the checksum is used for Outline how the c

  8. Q10.1

    June 2023 · Paper 2

    1 mark4.5.5 Information coding systems4.9.1 Communication
    The whole paper ↗
    June 2023 Paper 2, question 10.1: A data communication system uses asynchronous data transmission with even parity to send character codes that are encoded using 7-bit ASCII. Figure 9 shows five

  9. Q10.3

    June 2023 · Paper 2

    1 mark4.5.5 Information coding systems
    The whole paper ↗
    June 2023 Paper 2, question 10.3: Describe one limitation of the use of parity bits for managing errors. [1 mark]

  10. Q04.1

    June 2023 · AS Paper 2

    1 mark4.5.5 Information coding systems
    The whole paper ↗
    June 2023 AS Paper 2, question 04.1: Explain why it is better for a majority voting system to send each bit five times instead of four. [1 mark]

  11. Q04.2

    June 2023 · AS Paper 2

    2 marks4.5.5 Information coding systems
    The whole paper ↗
    June 2023 AS Paper 2, question 04.2: Give two reasons why using a parity bit system might be preferred to using majority voting when transmitting data. [2 marks]

  12. Q04.3

    June 2023 · AS Paper 2

    1 mark4.5.5 Information coding systems
    The whole paper ↗
    June 2023 AS Paper 2, question 04.3: Figure 2 shows a bit pattern that a computer has received. Each byte contains a 7-bit ASCII code with a parity bit. The method used when transmitting data was o

  13. Q04.1

    June 2022 · AS Paper 2

    1 mark4.5.5 Information coding systems
    The whole paper ↗
    June 2022 AS Paper 2, question 04.1: ASCII is one character coding system. Explain the term ‘character code’. [1 mark]

  14. Q04.2

    June 2022 · AS Paper 2

    2 marks4.5.5 Information coding systems
    The whole paper ↗
    June 2022 AS Paper 2, question 04.2: Explain why Unicode was introduced as an alternative to ASCII. [2 marks]

  15. Q04.3

    June 2022 · AS Paper 2

    2 marks4.5.5 Information coding systems
    The whole paper ↗
    June 2022 AS Paper 2, question 04.3: Describe how the parity bit would be generated for the character code in Figure 3 using even parity. [2 marks]

  16. Q04.4

    June 2022 · AS Paper 2

    1 mark4.5.5 Information coding systems
    The whole paper ↗
    June 2022 AS Paper 2, question 04.4: Write the parity bit below to complete the byte that will be sent using even parity. [1 mark] 0 0 1 0 1 1 1

  17. Q01.3

    November 2020 · AS Paper 2

    1 mark4.5.5 Information coding systems
    The whole paper ↗
    November 2020 AS Paper 2, question 01.3: A data transmission system transmits one byte of data, using the majority voting system for error correction. Figure 1 shows the bit pattern that was received.

  18. Q01.4

    November 2020 · AS Paper 2

    2 marks4.5.5 Information coding systems
    The whole paper ↗
    November 2020 AS Paper 2, question 01.4: A check digit can be used to detect errors when data are entered or transmitted. Explain what a check digit is and outline how the check digit is generated. [2

  19. Q10.3

    November 2020 · AS Paper 2

    2 marks4.5.5 Information coding systems
    The whole paper ↗
    November 2020 AS Paper 2, question 10.3: A data transmission system uses even parity. Data are transmitted in bytes, with each byte containing seven data bits and one parity bit. Explain how the receiv
All 19 questions on Information coding systems, as a list
  1. June 2025, AS Paper 2, Q03.1 (1 mark): The character Q has the binary representation 1010001 in ASCII. What is the binary representation of the character T in ASCII? [1 mark]
  2. June 2025, AS Paper 2, Q03.2 (1 mark): Unicode was introduced to overcome some of the limitations of ASCII. State one limitation of ASCII that Unicode overcomes. [1 mark]
  3. June 2025, AS Paper 2, Q07.2 (2 marks): State the type of parity that is computed by the logic circuit in Figure 3 and give a reason for your answer. [2 marks] Type of parity Reason
  4. June 2025, AS Paper 2, Q07.3 (3 marks): Alice wants to send a 4-bit message to Bob but is worried about errors. Alice decides to use a parity bit to allow some error checking. Describe how Alice can s
  5. June 2025, AS Paper 2, Q07.4 (1 mark): Describe one limitation of using a parity bit for error detection. [1 mark]
  6. June 2024, Paper 2, Q10.2 (2 marks): The value in memory location 130 before the program is executed is the program’s input and the value stored in memory location 130 when the program finishes exe
  7. June 2023, Paper 2, Q02.2 (2 marks): Explain what the checksum is used for and outline how the checksum’s value will be determined. [2 marks] Explain what the checksum is used for Outline how the c
  8. June 2023, Paper 2, Q10.1 (1 mark): A data communication system uses asynchronous data transmission with even parity to send character codes that are encoded using 7-bit ASCII. Figure 9 shows five
  9. June 2023, Paper 2, Q10.3 (1 mark): Describe one limitation of the use of parity bits for managing errors. [1 mark]
  10. June 2023, AS Paper 2, Q04.1 (1 mark): Explain why it is better for a majority voting system to send each bit five times instead of four. [1 mark]
  11. June 2023, AS Paper 2, Q04.2 (2 marks): Give two reasons why using a parity bit system might be preferred to using majority voting when transmitting data. [2 marks]
  12. June 2023, AS Paper 2, Q04.3 (1 mark): Figure 2 shows a bit pattern that a computer has received. Each byte contains a 7-bit ASCII code with a parity bit. The method used when transmitting data was o
  13. June 2022, AS Paper 2, Q04.1 (1 mark): ASCII is one character coding system. Explain the term ‘character code’. [1 mark]
  14. June 2022, AS Paper 2, Q04.2 (2 marks): Explain why Unicode was introduced as an alternative to ASCII. [2 marks]
  15. June 2022, AS Paper 2, Q04.3 (2 marks): Describe how the parity bit would be generated for the character code in Figure 3 using even parity. [2 marks]
  16. June 2022, AS Paper 2, Q04.4 (1 mark): Write the parity bit below to complete the byte that will be sent using even parity. [1 mark] 0 0 1 0 1 1 1
  17. November 2020, AS Paper 2, Q01.3 (1 mark): A data transmission system transmits one byte of data, using the majority voting system for error correction. Figure 1 shows the bit pattern that was received.
  18. November 2020, AS Paper 2, Q01.4 (2 marks): A check digit can be used to detect errors when data are entered or transmitted. Explain what a check digit is and outline how the check digit is generated. [2
  19. November 2020, AS Paper 2, Q10.3 (2 marks): A data transmission system uses even parity. Data are transmitted in bytes, with each byte containing seven data bits and one parity bit. Explain how the receiv

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