Free Logic gates & circuits questions for IGCSE Computer Science (0478), part of Databases & logic. Each question has the answer and the marking points an examiner would look for.
Generate a full Logic Gates & Circuits worksheet →All Databases & logic questionsFig. 1.1 shows a logic circuit.
Complete the truth table for this logic circuit.
| A | B | C | 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 |
Write a logic expression for this circuit.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | X column: 01101010 8 correct outputs B4 B3 for 6–7 correct, B2 for 4–5, B1 for 2–3 | 4 |
| (b) | X = (A OR B) XOR C (A OR B) B1 XOR C B1 | 2 |
Complete the truth table for the logic expression
X = (NOT A AND B) NOR C
| A | B | C | 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 |
State how many logic gates are needed to draw this circuit, and name them.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | X column: 10001010 8 correct outputs B4 B3 for 6–7 correct, B2 for 4–5, B1 for 2–3 | 4 |
| (b) | 3: NOT, AND, NOR 3 gates B1 NOT, AND and NOR B1 | 2 |
State what is meant by the term NAND gate.
| Part | Answer and marking points | Marks |
|---|---|---|
| A gate whose output is 0 only when both inputs are 1 A gate whose output is 0 only when both inputs are 1 B1 | 1 |
Complete the truth table for the logic expression
X = (NOT A OR B) AND C
| A | B | C | 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 |
State how many logic gates are needed to draw this circuit, and name them.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | X column: 01010001 8 correct outputs B4 B3 for 6–7 correct, B2 for 4–5, B1 for 2–3 | 4 |
| (b) | 3: NOT, OR, AND 3 gates B1 NOT, OR and AND B1 | 2 |
Complete the truth table for the logic expression
X = (NOT A NOR B) NAND C
| A | B | C | 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 |
State how many logic gates are needed to draw this circuit, and name them.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | X column: 11111011 8 correct outputs B4 B3 for 6–7 correct, B2 for 4–5, B1 for 2–3 | 4 |
| (b) | 3: NOT, NOR, NAND 3 gates B1 NOT, NOR and NAND B1 | 2 |
Complete the truth table for the logic expression
X = (A NAND B) AND C
| A | B | C | 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 |
State how many logic gates are needed to draw this circuit, and name them.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | X column: 01010100 8 correct outputs B4 B3 for 6–7 correct, B2 for 4–5, B1 for 2–3 | 4 |
| (b) | 2: NAND, AND 2 gates B1 NAND and AND B1 | 2 |
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Meet Riyaz →Original Cambridge-style practice questions written for mentorriyaz.in. These are not Cambridge past paper questions, and this site is not affiliated with or endorsed by Cambridge University Press & Assessment. Updated 2026-11-04. Paper generator · mentorriyaz.in