3 Consider the logic statement: X = ((((NOT A AND B) OR C) AND B) NOR (B OR C)) (a) Draw a logic circuit to represent the given logic statement. Do not attempt to simplify the statement. All logic gates must have a maximum of two inputs. X B A C [6] (b) Consider the completed truth table for the given logic statement. Row number A B C Working space X 1 0 0 0 1 2 0 0 1 1 3 0 1 0 1 4 0 1 1 0 5 1 0 0 1 6 1 0 1 0 7 1 1 0 1 8 1 1 1 1 There are four errors in the truth table in the output (X) column. Identify the four incorrect outputs. Write the row number to identify each incorrect output. Row … Row … Row … Row … [4]

3(a) One mark for each correct logic gate with correct input. 6 3(b) One mark per each correct row. − Row 2 − Row 3 − Row 7 − Row 8 4 (a) You earn marks by drawing a logic circuit that accurately represents the given logic statement, ensuring each gate has a maximum of two inputs and all inputs are correctly connected. (b) You must identify the four specific row numbers in the truth table where the output (X) is incorrect.

5 Computers use logic gates. (a) State the single logic gate that produces each truth table. Truth table Logic gate A B Output 0 0 1 0 1 1 1 0 1 1 1 0 … A B Output 0 0 0 0 1 1 1 0 1 1 1 0 … A B Output 0 0 1 0 1 0 1 0 0 1 1 0 … [3] (b) An aeroplane has a warning system that monitors the height of the aeroplane above the ground, whether the aeroplane is ascending or descending, and the speed of the aeroplane. Input Binary value Condition Height (H) 1 Height is less than 500 metres 0 Height is greater than or equal to 500 metres Ascending or Descending (A) 1 Aeroplane is ascending or in level flight 0 Aeroplane is descending Speed (S) 1 Speed is less than or equal to 470 knots 0 Speed is greater than 470 knots The warning system will produce an output of 1 that will sound an alarm (W) when either of these conditions apply: Height is less than 500 metres and the aeroplane is descending or The aeroplane is descending and speed is greater than 470 knots Draw a logic circuit to represent the warning system. W A H S [5]

5(a) Truth table Logic gate A B Output 0 0 1 0 1 1 1 0 1 1 1 0 NAND [1] A B Output 0 0 0 0 1 1 1 0 1 1 1 0 XOR / Exclusive OR [1] A B Output 0 0 1 0 1 0 1 0 0 1 1 0 NOR [1] 3 5(b) One mark for each logic gates with correct inputs − NOT A − NOT S − H AND NOT A − NOT A AND NOT S − Final OR 5 (a) To earn marks, you must correctly identify the logic gate for each truth table: NAND for the first, XOR/Exclusive OR for the second, and NOR for the third. (b) You need to draw a logic circuit that accurately represents the given conditions for the warning system. This involves correctly implementing NOT gates for 'A' and 'S' (representing descending and speed > 470 knots), two AND gates for the two conditions, and a final OR gate to combine their outputs to produce 'W'. Each gate with correct inputs contributes to the marks.

6 Consider the logic statement: X = (((A AND B) OR (C AND NOT B)) XOR NOT C) (a) Draw a logic circuit to represent the given logic statement. Do not attempt to simplify the statement. All logic gates must have a maximum of two inputs. X B A C [6] (b) Consider the completed truth table for the given logic statement. Row number A B C Working space X 1 0 0 0 0 2 0 0 1 1 3 0 1 0 0 4 0 1 1 1 5 1 0 0 0 6 1 0 1 1 7 1 1 0 0 8 1 1 1 1 There are four errors in the truth table in the output (X) column. Identify the four incorrect outputs. Write the row number to identify each incorrect output. Row … Row … Row … Row … [4]

6(a) One mark per each correct logic gate, with correct input: 6 6(b) − Row 1 − Row 3 − Row 4 − Row 5 4 For 6(a), you must draw a logic circuit that accurately represents the given logic statement, ensuring each logic gate has a maximum of two inputs and all connections are correct. For 6(b), you need to identify and list the row numbers for the four specific incorrect outputs in the provided truth table's X column.

8 Consider the following logic circuit: A B C X (a) Two NOT gates are used in the given logic circuit. Identify three other logic gates that are used in the given logic circuit. 1 … 2 … 3 … [3] (b) Consider the completed truth table for the given logic circuit. Row number A B C Working space X 1 0 0 0 0 2 0 0 1 1 3 0 1 0 0 4 0 1 1 0 5 1 0 0 1 6 1 0 1 1 7 1 1 0 0 8 1 1 1 1 There are four errors in the truth table in the output (X) column. Identify the four incorrect outputs. Write the row number to identify each incorrect output. Row … Row … Row … Row … [4]

8(a) − AND − NOR − XOR 3 8(b) − Row 1 − Row 4 − Row 7 − Row 8 4

8 Consider the following logic statement: X = (((A OR B) AND (NOT(B XOR C))) OR NOT C) (a) Draw a logic circuit to represent the given logic statement. Do not attempt to simplify the logic statement. All logic gates must have a maximum of two inputs. A B X C [6] (b) Complete the truth table for the given logic statement. A B C 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 [4]

8(a) One mark per each correct logic gate with correct inputs . 6 8(b) 4 marks for 8 correct outputs 3 marks for 6/7 correct outputs 2 marks for 4/5 correct outputs 1 mark for 2/3 correct outputs A B C Working space X 0 0 0 1 0 0 1 0 0 1 0 1 0 1 1 1 1 0 0 1 1 0 1 0 1 1 0 1 1 1 1 1 4 For part (a), you earn one mark for each correctly drawn logic gate with its correct inputs, following the given logic statement without simplification. For part (b), marks are awarded based on the number of correct outputs in the truth table, with 4 marks for all 8 correct, down to 1 mark for 2 or 3 correct outputs.

Cambridge IGCSE Computer Science · 0478

IGCSE Computer Science (0478) Boolean logic past paper questions

Revise IGCSE Computer Science (0478) — Boolean logic with real Cambridge past-paper questions grouped by topic, each shown with its marking scheme. Working one topic at a time targets exactly the skill each question tests.

38 free questions from 2016–2021, each with its marking scheme. Open the full topical bank to filter by subtopic, paper, and year.