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Cambridge IGCSE Computer Science (Paper 2) Smart practice A mixed round aimed at your weak spots
Unit 7
Algorithm design and problem-solving
The program development life cycle
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Sub-systems, decomposition and structure diagrams
0%
Designing solutions with flowcharts
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Explaining the purpose of an algorithm
0%
Standard methods of solution
Linear search
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Bubble sort
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Totalling, counting, maximum, minimum and average
0%
Validation and verification
Validation checks
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Verification checks
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Test data
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Trace tables
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Finding and correcting errors in algorithms
0%
Writing and amending algorithms
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Unit 8
Programming
Programming concepts
Variables, constants and data types
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Input, output and sequence
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Selection: IF and CASE statements
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Iteration: FOR, REPEAT and WHILE loops
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String handling
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Arithmetic, relational and logical operators
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Nested statements
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Procedures, functions and parameters
0%
Library routines: MOD, DIV, ROUND and RANDOM
0%
Maintainable programs
0%
Arrays
1D and 2D arrays
0%
File handling
File handling
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Unit 9
Databases
Single-table databases, data types and primary keys
0%
SQL queries
0%
Unit 10
Boolean logic
Logic gates and their functions
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Logic circuits
0%
Truth tables
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Logic expressions
0%
Unit 11
Exam practice
15-mark scenario questions
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Truth tables

Practise 33 exam-style questions on Truth tables for Cambridge IGCSE Computer Science (Paper 2). Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.

  • 33 questions
  • 1–6 marks each
  • Instant marking
  • No sign-up needed
20 questions, marked as you go

Sample questions with model answers

Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.

Question 1

1 mark

Look at the logic circuit shown.

State the value of X in the row of its truth table where A = 1, B = 1 and C = 0.

Logic circuit with three inputs, A, B and C, on the left and one output, X, on the right. It has three logic gates (numbered here from left to right, then top to bottom): gate 1 is a NOT gate with input B; gate 2 is an AND gate with inputs from input A (upper) and gate 1 (lower); gate 3 is a NOR gate with inputs from gate 2 (upper) and input C (lower), and its output is X. As a logic expression: X = (A AND (NOT B)) NOR C.

Model answer

X = 1

Explanation

NOT B = 0, so A AND (NOT B) = 1 AND 0 = 0. The NOR gate then gives NOT (0 OR 0) = 1, as C = 0. Working gate by gate from the inputs avoids mistakes.

Mark scheme
  1. 1 mark

    1

Question 2

2 marks

Look at the logic circuit shown.

Give the output X for the four rows of its truth table where A = 1, in binary order (A, B, C = 100, 101, 110, 111).

Logic circuit with three inputs, A, B and C, on the left and one output, X, on the right. It has three logic gates (numbered here from left to right, then top to bottom): gate 1 is an AND gate with inputs A and B; gate 2 is a NOT gate with input C; gate 3 is a NOR gate with inputs from gate 1 (upper) and gate 2 (lower), and its output is X. As a logic expression: X = (A AND B) NOR (NOT C).

Model answer

0, 1, 0, 0

Explanation

The NOR gate gives 1 only when both its inputs, A AND B and NOT C, are 0. For 100, NOT C = 1 so X = 0; for 101 both are 0 so X = 1; for 110 both are 1 so X = 0; for 111, A AND B = 1 so X = 0.

Mark scheme
  1. 1 mark

    Rows 100 and 101: 0, 1

    1 mark for each pair of correct rows

  2. 1 mark

    Rows 110 and 111: 0, 0

Question 3

4 marks

The truth table shown is for the logic expression
X = (A OR B) AND (NOT C)

Give the values in the X column, from the first row (000) to the last row (111).

Truth table with three input columns, A, B and C, and two further columns, "Working space" and X (a thick line separates the inputs from the rest). The 8 rows list every combination of inputs in binary order from 000 to 111. The X column is blank in every row, to be completed. The "Working space" column is empty, as space for working.

Model answer

0, 0, 1, 0, 1, 0, 1, 0

Explanation

X is 1 when at least one of A and B is 1 and C is 0. So every row with C = 1 gives 0, and of the rows with C = 0, only 000 fails (A OR B = 0). Working columns for A OR B and NOT C help avoid errors.

Mark scheme
  1. 1 mark

    Rows 000 and 001: 0, 0

    1 mark for each pair of correct rows

  2. 1 mark

    Rows 010 and 011: 1, 0

  3. 1 mark

    Rows 100 and 101: 1, 0

  4. 1 mark

    Rows 110 and 111: 1, 0

Question 4

4 marks

A laptop cooling fan F is controlled by three inputs:
H = 1 when the processor is hot
L = 1 when the lid is closed
Z = 1 when the laptop is asleep

The fan runs (F = 1) when the processor is hot, unless the lid is closed and the laptop is asleep at the same time.

The truth table shown is for this fan. Give the values in the F column, from the first row to the last.

Truth table with three input columns, H, L and Z, and two further columns, "Working space" and F (a thick line separates the inputs from the rest). The 8 rows list every combination of inputs in binary order from 000 to 111. The F column is blank in every row, to be completed. The "Working space" column is empty, as space for working.

Model answer

0, 0, 0, 0, 1, 1, 1, 0

Explanation

F = H AND (L NAND Z): the processor must be hot, and the lid and sleep inputs must not both be 1. So the fan never runs when H = 0, and when H = 1 it runs except in row 111.

Mark scheme
  1. 1 mark

    Rows 000 and 001: 0, 0

    1 mark for each pair of correct rows (inputs in the order H, L, Z)

  2. 1 mark

    Rows 010 and 011: 0, 0

  3. 1 mark

    Rows 100 and 101: 1, 1

  4. 1 mark

    Rows 110 and 111: 1, 0

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