Computer Science · May / June 2024 · Paper 22 · Question 8
0478
As printed in the paper
The question as text
A logic circuit is to be built to control the opening of a safe used to store money. There are two keys, A and B, and a time switch C. The safe can only open if both keys are used and the time switch is off. key A not used 0 used 1 key B not used 0 used 1 time switch C switch off 0 switch on 1 safe X safe cannot open 0 safe can open 1
Read automatically from the paper; the printed page above is exact.
Show the answer and mark scheme
8(a)[3]
X = 1 mark
(A AND B) // A AND B 1 mark
AND NOT C 1 mark
X = (A AND B) AND NOT C
8(b)[4]
Four marks for 8 correct outputs
Three marks for 6/7 correct outputs
Two marks for 4/5 correct outputs
One mark for 2/3 correct outputs
A
B
C
X
0
0
0
0
0
0
1
0
0
1
0
0
0
1
1
0
1
0
0
0
1
0
1
0
1
1
0
1
1
1
1
0
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