This key facts covers Example 1: (A AND B) OR C within Truth Tables for GCSE Computer Science. Revise Truth Tables in 3.4 Computer Systems for GCSE Computer Science with 15 exam-style questions and 15 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 5 of 11 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Example 1: (A AND B) OR C
This circuit has TWO gates: First an AND gate combining A and B, then an OR gate combining that result with C.
| A | B | C | A AND B (intermediate) |
(A AND B) OR C (final output) |
| 0 | 0 | 0 | 0 | 0 |
| 0 | 0 | 1 | 0 | 1 |
| 0 | 1 | 0 | 0 | 0 |
| 0 | 1 | 1 | 0 | 1 |
| 1 | 0 | 0 | 0 | 0 |
| 1 | 0 | 1 | 0 | 1 |
| 1 | 1 | 0 | 1 | 1 |
| 1 | 1 | 1 | 1 | 1 |
Intermediate column (A AND B): Only shows 1 when BOTH A and B are 1 (row 7 and 8)
Final output: Shows 1 when EITHER the intermediate is 1 OR C is 1 (rows 2, 4, 6, 7, 8)
In plain English: Output is 1 if "A and B are both true" OR "C is true"
Practice questions for Truth Tables
How many rows are needed in a truth table with 2 inputs (not including the header row)?
Explain why truth tables are useful when designing or testing logic circuits.