Logic Revision
AQA AS-Level Computing COMP2
2014
98 minutes
95 marks
Page 1 of 40
,Q1.
The figure below shows a logic circuit.
(a) Complete the truth table below for the logic circuit shown in the above figure. Write the
correct value of the output Q for each of the listed sets of inputs.
Input Input Input Output
A B C Q
1 0 1
0 1 0
0 1 1
(3)
(b) Two of the gates in the circuit shown in the above figure could be replaced by a single
gate.
(i) Which two gates could be replaced?
...............................................................................................................
(1)
(ii) What single gate would be used instead?
...............................................................................................................
(1)
(c) Why is it an advantage to use as few gates as possible in a logic circuit?
(1)
(Total 6 marks)
Page 2 of 40
,Q2.
(a) State the names of the logic gates represented by each of the three truth tables below.
Input A Input B Output
0 0 0
0 1 0 Logic gate name ....................................
1 0 0
1 1 1
Input A Input B Output
0 0 1
0 1 0 Logic gate name ....................................
1 0 0
1 1 0
Input A Input B Output
0 0 0
0 1 1 Logic gate name ....................................
1 0 1
1 1 0
(3)
(b) Simplify the following Boolean expressions.
(i) B . (A+ )
...............................................................................................................
...............................................................................................................
(1)
(ii) A.B+B
...............................................................................................................
...............................................................................................................
(1)
(iii)
...............................................................................................................
...............................................................................................................
(2)
Page 3 of 40
, (c) Draw a logic circuit for the following Boolean expression:
Q = (A ⊕ B) . B
You will need to make use of the symbols below when drawing your logic circuit.
(2)
(Total 9 marks)
Q3.
The diagram below shows two masking operations.
(a) Give the content of Result 1 when Mask 1 is applied to Test using the AND operation.
.......................................................................................................................
(1)
(b) What logical operation must be used to produce Result 2 when Mask 2 is applied to Set?
.......................................................................................................................
(1)
(Total 2 marks)
Page 4 of 40
AQA AS-Level Computing COMP2
2014
98 minutes
95 marks
Page 1 of 40
,Q1.
The figure below shows a logic circuit.
(a) Complete the truth table below for the logic circuit shown in the above figure. Write the
correct value of the output Q for each of the listed sets of inputs.
Input Input Input Output
A B C Q
1 0 1
0 1 0
0 1 1
(3)
(b) Two of the gates in the circuit shown in the above figure could be replaced by a single
gate.
(i) Which two gates could be replaced?
...............................................................................................................
(1)
(ii) What single gate would be used instead?
...............................................................................................................
(1)
(c) Why is it an advantage to use as few gates as possible in a logic circuit?
(1)
(Total 6 marks)
Page 2 of 40
,Q2.
(a) State the names of the logic gates represented by each of the three truth tables below.
Input A Input B Output
0 0 0
0 1 0 Logic gate name ....................................
1 0 0
1 1 1
Input A Input B Output
0 0 1
0 1 0 Logic gate name ....................................
1 0 0
1 1 0
Input A Input B Output
0 0 0
0 1 1 Logic gate name ....................................
1 0 1
1 1 0
(3)
(b) Simplify the following Boolean expressions.
(i) B . (A+ )
...............................................................................................................
...............................................................................................................
(1)
(ii) A.B+B
...............................................................................................................
...............................................................................................................
(1)
(iii)
...............................................................................................................
...............................................................................................................
(2)
Page 3 of 40
, (c) Draw a logic circuit for the following Boolean expression:
Q = (A ⊕ B) . B
You will need to make use of the symbols below when drawing your logic circuit.
(2)
(Total 9 marks)
Q3.
The diagram below shows two masking operations.
(a) Give the content of Result 1 when Mask 1 is applied to Test using the AND operation.
.......................................................................................................................
(1)
(b) What logical operation must be used to produce Result 2 when Mask 2 is applied to Set?
.......................................................................................................................
(1)
(Total 2 marks)
Page 4 of 40
