4.5.5.3 Error checking and correction Quiz: AQA Computer Science, Unit 5

The 20 questions

1. What extra bit is added to data to ensure the total count of 1s is even or odd?

   • Checksum
   • Parity bit
   • Check digit
   • Start bit

2. Which error detection technique sends multiple copies of bits and determines values by majority?

   • Parity checking
   • Checksum calculation
   • Majority voting
   • Check digit validation

3. What calculated value derived from a block of data is sent with it to detect corruption?

   • Parity bit
   • Checksum
   • Opcode
   • Majority vote

4. What is the final digit added to data such as ISBNs to detect human entry errors?

   • Parity bit
   • Stop bit
   • Checksum
   • Check digit

5. Which error checking method adds a single bit to each byte?

   • Check digit
   • Checksum
   • Majority voting
   • Parity checking

6. What type of bit errors cannot be detected by a single parity bit scheme?

   • Total signal loss
   • Odd number of flips
   • Single bit flip
   • Even number of flips

7. Which error checking technique can correct bit errors without requesting data retransmission?

   • Majority voting
   • Check digit
   • Parity bit
   • Checksum

8. What is the even parity bit for the 7-bit binary value 1011001?

   • 4
   • 0
   • 1
   • 7

9. What is the odd parity bit for the 7-bit binary string 1010101?

   • 4
   • 0
   • 1
   • 5

10. Three copies of a bit arrive as 1, 0, and 1. Which value does majority voting output?

    • 0
    • 0.5
    • 1
    • 2

11. Data bytes 10, 20 and 30 are summed modulo 256 to form a checksum. What is the checksum?

    • 70
    • 600
    • 60
    • 50

12. Can a single parity bit detect an error if exactly two bits are flipped during transmission?

    • Only odd parity
    • Sometimes
    • No
    • Yes

13. Five copies of a bit arrive as 1, 0, 1, 1, and 0. Which value is selected by majority voting?

    • 5
    • 3
    • 0
    • 1

14. Digits 4, 7 and 2 have a check digit equal to their sum modulo 10. What is the check digit?

    • 3
    • 2
    • 13
    • 9

15. An 8-bit checksum is the sum of bytes 200 and 100 modulo 256. What is the checksum?

    • 100
    • 56
    • 300
    • 44

16. Which main advantage does majority voting have over a single parity bit system?

    • It saves bandwidth
    • Detects even errors
    • It corrects errors
    • Uses fewer bits

17. In a 3-bit majority voting system, what happens if two copies are corrupted identically?

    • Transmission rejected
    • Correct value selected
    • Corrupted value accepted
    • Error detected, fixed

18. Why might a checksum check fail to detect data corruption in a received block?

    • Same checksum produced
    • Parity bit inverted
    • Data length changed
    • Checksum too long

19. Which type of transmission error is always detected by a single parity bit?

    • Single bit flip
    • Four bit flips
    • Transposed adjacent bits
    • Two bit flips

20. Which error is undetected by a check digit calculated as the simple sum of digits modulo 10?

    • Deleting a digit
    • Changing a digit
    • Adding extra digits
    • Swapping two digits

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