Boolean Logic · 5 question types
Past paper frequency (2018 to 2024)
This topic accounts for approximately 6% of your exam marks.
Writing Boolean expressions from logic diagrams and simplifying using laws appear regularly.
The three representations of a Boolean function can be converted in any direction. Each conversion has been covered above, but it helps to see them together.
| From → to | Method (covered in) |
|---|---|
| Circuit → expression | Label each gate's output with its sub-expression, working left to right (section 3). |
| Truth table → expression | Sum-of-products: one AND term per Q = 1 row, OR them together (section 4). |
| Expression → truth table | Evaluate the expression for every possible combination of inputs (section 5, repeated for each row). |
| Expression → circuit | One gate per operator; bracket innermost first; NOT gates before the negated signal feeds its next gate (covered in topic 26). |
| Circuit → truth table | Trace signals through each gate for every input row, adding intermediate columns (covered in topic 26). |
| Truth table → circuit | Derive the SoP expression, then draw the circuit for that expression. |
Whatever route the exam asks for, the key check is the same: at the end, the truth table of the new representation must agree with the truth table of the original, row for row.