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Computer Science · May / June 2026 · Paper 12 · Question 4

0478

As printed in the paper

The question as text

An odd parity byte check is used to check for errors in data that is transmitted from a computer to a printer.

Read automatically from the paper; the printed page above is exact.

Show the answer and mark scheme

  • 4(a)[3]

    One mark for each correct parity bit.

    1
    1
    1

  • 4(b)(i)[2]

    Two from:

    A transposition error has occurred // Bits have been interchanged/changed places // Even number of bits has flipped/changed // bits are out of order // doesn’t record the location of bits
    … so count/total of the 1s/0s in the byte is still odd/the same // still has an odd number of 1s/0s
    … so it will still meet the parity set

  • 4(b)(ii)[2]

    Two from:

    Parity block check
    Even parity (byte) check
    Checksum
    Echo check
    Automatic repeat query/request // ARQ

  • 4(c)(i)[1]

    One from:

    Symmetric // synchronous
    Asymmetric // asynchronous

  • 4(c)(ii)[1]

    One from:

    A string of characters/numbers used to encrypt data
    Used by an algorithm/cipher (to encrypt/decrypt the data)

  • 4(c)(iii)[1]

    Cipher/cypher text

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