Boolean Logic and Expressions
Boolean Logic · 5 question types
Exam Frequency Analysis
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.
Topic 26 covered the six logic gates as physical components: AND, OR, NOT, XOR, NAND, NOR. This topic covers the same gates as algebra: how to write them as expressions, derive them from circuits or truth tables, and evaluate them for given inputs.
A Boolean expression is an algebraic statement built from Boolean variables (each
0or1), the operators AND, OR and NOT, and brackets. Every expression evaluates to a single Boolean value,0or1.
The output of a logic circuit can always be written as a Boolean expression in its inputs. Working the other way, every Boolean expression has a corresponding logic circuit and a corresponding truth table. The three representations are interchangeable; choosing the right one for a question is half the work.