These are some O level Past Papers questions of Logic Gates for people who have difficulty in solving them...

1. General Certificate of Education Ordinary Level COMPILED BY: ABDUL MOIZ
CAMBRIDGE INTERNATIONAL EXAMINATIONS
COMPUTER STUDIES 2210/1
Logic Gates
Summer 2014 P1 (Q7) ………………………………………………………………………………………………………………………………. 1
Summer 2014 P1 (Q7).....................................................................................................................................1
Specimen 2015 P1 (Q3)...................................................................................................................................4
Summer 2013 P11 (Q10).................................................................................................................................6
Summer 2013 P12 (Q15).................................................................................................................................6
Winter 2012 P12 (Q11)...................................................................................................................................7
Winter 2012 P13 (Q15)...................................................................................................................................8
Summer 2012 P11 (Q12).................................................................................................................................8
Summer 2012 P12 (Q10).................................................................................................................................9
Winter 2011 P11 (Q14).................................................................................................................................10
Summer 2011 P11 (Q10)...............................................................................................................................12
Specimen 2011 P1 (Q11)...............................................................................................................................13
Specimen 2011 P1 (Q12)...............................................................................................................................13
Summer 2014 P1 (Q7)
Q. (a) Draw the logic circuit for the logic statement:
X = 1 if (L is NOT 1 AND F = 1) OR (F is NOT 1 AND A is 1)
Computer-2210 (Bit Pattern) (1) abdul.moiz99@yahoo.com

2. [5]
(b) Complete the truth table for the above system.
L F A
Working space
X
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
S O L U T I O N:
(a) 1 mark per correct logic gate (accept other gate symbols)
Computer-2210 (Bit Pattern) (2) abdul.moiz99@yahoo.com
L
F X
A

3. Computer-2210 (Bit Pattern) (3) abdul.moiz99@yahoo.com

4. Specimen 2015 P1 (Q3)
An alarm, Y, sends a signal (Y = 1) when certain fault conditions in a chemical process are detected. The inputs
are:
Computer-2210 (Bit Pattern) (4) abdul.moiz99@yahoo.com
L F A X
0 0 0 0
0 0 1 1
0 1 0 1
0 1 1 1
1 0 0 0
1 0 1 1
1 1 0 0
1 1 1 0

5. The alarm, Y, returns a value of 1 if:
either temperature >= 120o
C AND stirrer bar is OFF
or acidity > 5 AND temperature < 120o
C
(a) Draw the logic circuit for the above system using these logic gates. [5]
Computer-2210 (Bit Pattern) (5) abdul.moiz99@yahoo.com

6. (b) Complete the truth table for this alarm system. [4]
A T S Y
1 1 1
1 1 0
1 0 1
1 0 0
0 1 1
0 1 0
0 0 1
0 0 0
Summer 2013 P11 (Q10)
(a) (i) Complete the truth table for the logic circuit which is made up of NAND gates only. [2]
(ii) What single logic gate has the same function as the above logic circuit? [1]
(b) (i) Complete the truth table for the logic circuit.
(ii) What could replace the whole logic circuit? [1]
Summer 2013 P12 (Q15)
(a) Draw the logic circuit represented by the logic statement:
X = 1 if (B is NOT 1 AND S is NOT 1) OR (P is NOT 1 AND S is 1) [6]
Computer-2210 (Bit Pattern) (6) abdul.moiz99@yahoo.com

7. b) Complete the truth table for the above logic statement. [4]
Winter 2012 P12 (Q11)
An alarm sounds when certain conditions occur in a nuclear reactor.
The output, X, of a logic circuit that drives the alarm must have a value of 1 if:
either carbon dioxide pressure too low and temperature < = 300°C
or water pressure > 10 bar and temperature > 300°C
The inputs to the system are:
(a) Draw the required logic circuit using AND, OR and NOT gates only. [5]
(b) Complete the truth table for the above system. [4]
P T W X
1 1 1
1 1 0
1 0 1
1 0 0
0 1 1
0 1 0
0 0 1
0 0 0
Computer-2210 (Bit Pattern) (7) abdul.moiz99@yahoo.com

8. Winter 2012 P13 (Q15)
15 (a) Complete the truth table for the following logic circuit: [4]
A B C X
1 1 1
1 1 0
1 0 1
1 0 0
0 1 1
0 1 0
0 0 1
0 0 0
(b) The above logic circuit uses AND, OR and NOT gates.
Name another logic gate and complete its truth table. [3]
Name : _______________________________________________
Summer 2012 P11 (Q12)
(a) (i) Complete the truth table for the following logic circuit, which is made up of NAND gates:
Computer-2210 (Bit Pattern) (8) abdul.moiz99@yahoo.com

9. (ii) What single logic gate has the same function as the above logic circuit? [1]
b) Complete the truth table for the following logic circuit:
A B C X
1 1 1
1 1 0
1 0 1
1 0 0
0 1 1
0 1 0
0 0 1
0 0 0
Summer 2012 P12 (Q10)
(a) Complete the truth table for the following logic circuit, which is made up of NAND gates:
A B C X
1 1 1
1 1 0
1 0 1
1 0 0
0 1 1
0 1 0
0 0 1
0 0 0
(b) Name two other types of logic gates and complete their associated truth tables:
Computer-2210 (Bit Pattern) (9) abdul.moiz99@yahoo.com

10. Winter 2011 P11 (Q14)
An alarm, X, gives a signal (i.e. X = 1) when a car fuel injection system gives certain fault conditions.
The inputs are:
The alarm returns a value of 1 if:
Either (i) pressure < 5 bar AND revs > 8000 rpm
or (ii) revs <= 8000 rpm AND temp > 120 °C
(a) Draw the logic circuit for the above system using these logic gates.
(b) Complete the truth table for this alarm system.
P R T X
1 1 1
Computer-2210 (Bit Pattern) (10) abdul.moiz99@yahoo.com

11. 1 1 0
1 0 1
1 0 0
0 1 1
0 1 0
0 0 1
0 0 0
Computer-2210 (Bit Pattern) (11) abdul.moiz99@yahoo.com

12. Summer 2011 P11 (Q10)
(a) Two logic gates are the AND gate and the OR gate. Complete the truth tables for these two gates:
(b) Complete the truth table for the following logic circuit:
A B C X
1 1 1
1 1 0
1 0 1
1 0 0
0 1 1
0 1 0
0 0 1
0 0 0
Computer-2210 (Bit Pattern) (12) abdul.moiz99@yahoo.com

13. Specimen 2011 P1 (Q11)
Draw the truth table for the following logic network: [4]
A B C X
1 1 1
1 1 0
1 0 1
1 0 0
0 1 1
0 1 0
0 0 1
0 0 0
Specimen 2011 P1 (Q12)
Draw a logic network and truth table for the following logic problem:
“A sprinkler (S) is ON if
either temperature alarm (T) is ON and cooler alarm (C) is ON
or vent alarm (V) is OFF and cooler alarm (C) is ON” [9]
Working: ____________________________________________________________________
____________________________________________________________________________ [2]
Logic Network:
Truth Table:
T C V S
1 1 1
1 1 0
1 0 1
1 0 0
0 1 1
0 1 0
0 0 1
0 0 0
Computer-2210 (Bit Pattern) (13) abdul.moiz99@yahoo.com