Computer Science · Oct / Nov 2016 · Paper 12 · Question 4
2210
As printed in the paper
The question as text
Nine bytes of data are transmitted from one computer to another. Even parity is used. An additional parity byte is also sent. The ten bytes arrive at the destination computer as follows: parity bit bit 2 bit 3 bit 4 bit 5 bit 6 bit 7 bit 8 byte 1 1 1 1 0 1 1 1 0 byte 2 0 0 0 0 0 1 0 1 byte 3 0 1 1 1 1 0 0 0 byte 4 1 1 0 0 0 0 0 0 byte 5 1 0 1 1 1 1 1 0 byte 6 0 1 0 1 1 0 0 1 byte 7 0 1 1 1 0 0 1 1 byte 8 0 0 1 1 0 1 1 0 byte 9 1 1 0 0 0 0 1 1 parity byte 0 0 1 0 0 0 1 0 One of the bits was corrupted during the data transmission.
Read automatically from the paper; the printed page above is exact.
Show the answer and mark scheme
4(a)[1]
Intersection of Row 7 and column 4 circled [1]
4(b)[2]
– Row (byte number) 7 has an odd number of 1s (five 1s) – Column (bit number) 4 has an odd number of 1s (five 1s) [2]
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