Boolean logic — IGCSE Computer Science (0478) questions by topic
Boolean logic questions ask candidates to link logic gate symbols to their functions, draw a logic circuit built strictly from a two-term expression combining AND, OR, NOT and XOR without simplifying it, and work through truth tables using a maximum of two inputs per gate. Complete, draw, identify, write and state are the command words, with draw meaning a circuit built strictly to the given expression, not a simplified version.
This page holds 19 real questions from 2023 to 2025 papers, worth 1 to 11 marks. Because a single misdrawn gate symbol changes an entire circuit's logic, submitting your diagrams for instant marking helps you spot an XOR gate drawn incorrectly, or an error made partway through a truth table, before it affects every line that follows.
What examiners look for
- Examiners repeatedly find the XOR gate drawn incorrectly, with many different variations seen, and errors made when working through a logic expression leading to incorrect outputs.
- Most candidates answered these questions well, correctly drawing gate symbols in the right order and applying the correct gate symbols with the correct inputs.
- Reports note that most candidates achieved all the marks available for completing a truth table.
May–June 2025, Paper 21
Consider the logic expression: X = (A AND B) XOR (B OR NOT C) Draw a logic circuit for this logic expression. Each logic gate must have a maximum of two inputs. Do not simplify…
Answer this question and get it marked →May–June 2025, Paper 22
Draw the symbol for an XOR logic gate and complete the truth table for it. XOR logic gate symbol: (draw in the box provided) Truth table: A B X --- --- --- 0 0 0 1 1 0 1 1
Answer this question and get it marked →May–June 2025, Paper 23
Draw the symbol for a NOR logic gate and complete the truth table for it. NOR logic gate symbol: (draw in the space provided) Truth table: A B Z --- --- --- 0 0 0 1 1 0 1 1
Answer this question and get it marked →May–June 2024, Paper 21
Consider the logic expression: Z = (R OR NOT T) XOR (NOT S AND T) Draw a logic circuit for this logic expression. Each logic gate must have a maximum of two inputs. Do not…
Answer this question and get it marked →May–June 2024, Paper 22
Four logic functions and five standard symbols for logic gates are shown. Draw one line to link each logic function to its standard symbol. Not all standard symbols will be used.…
Answer this question and get it marked →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…
Answer this question and get it marked →May–June 2024, Paper 23
Four logic gate symbols and five logic functions are shown. Draw one line to link each logic gate symbol to the appropriate logic function. Not all logic functions will be used.…
Answer this question and get it marked →October–November 2024, Paper 21
Tick (✓) one box to identify which option is used to show the inputs and output of a Boolean expression. [ ] A flowchart [ ] B trace table [ ] C truth table [ ] D variable
Answer this question and get it marked →Consider the logic circuit. Inputs X, Y, Z feed gates producing output W: input X through a NOT gate, ORed with the output of an XOR gate fed by Y and Z. Write a logic expression…
Answer this question and get it marked →October–November 2024, Paper 22
Consider the logic expression: X = (NOT P OR Q) NAND (Q XOR R) Draw a logic circuit for this logic expression. Each logic gate must have a maximum of two inputs. Do not simplify…
Answer this question and get it marked →October–November 2024, Paper 23
Four logic gates and five logic gate symbols are shown. Draw one line to link each logic gate to its correct symbol. Not all logic gate symbols will be used. Logic gates: AND,…
Answer this question and get it marked →A logic circuit is to be built to control the automatic opening of a window. The window W opens if the temperature T is too high, the heater H is off, and the air conditioning A…
Answer this question and get it marked →May–June 2023, Paper 21
Consider this logic expression: Z = (NOT A OR B) AND (B XOR C) Draw a logic circuit for this logic expression. Each logic gate must have a maximum of two inputs. Do not simplify…
Answer this question and get it marked →May–June 2023, Paper 22
Four logic gates and five standard symbols for logic gates are shown. Draw one line to link each logic gate to its standard symbol. Not all standard symbols will be used. Logic…
Answer this question and get it marked →Consider this logic expression: X = (A OR B) AND (NOT B AND C) Complete the truth table for this logic expression. A B C X --- --- --- --- 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1…
Answer this question and get it marked →May–June 2023, Paper 23
Consider the logic expression: Z is 1 if (A = 1 AND C = NOT 1) AND (B = 1 NOR C = 1) Draw a logic circuit for this logic expression. Each logic gate must have a maximum of two…
Answer this question and get it marked →October–November 2023, Paper 21
Consider this logic circuit. Inputs A, B, C feed gates producing output X. The circuit implements: input A through a NOT gate, ANDed with B, then ORed with NOT C. Write a logic…
Answer this question and get it marked →October–November 2023, Paper 22
Consider the logic expression: Z = (A NAND B) OR NOT (B XOR C) Draw a logic circuit for this logic expression. Each logic gate must have a maximum of two inputs. Do not simplify…
Answer this question and get it marked →October–November 2023, Paper 23
There are three descriptions of logic gates. Each logic gate has two inputs A and B with one output X. Identify each logic gate and complete a truth table for each. The only time…
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