Boolean Logic and Truth Tables
Evaluating AND, OR and NOT expressions, combining operators and constructing truth tables for decisions and digital systems.
How to study for GCSE Computer Science
Move repeatedly between problem, algorithm, trace, code, test evidence and system explanation; use the exact language and assessment format required by your current board.
Core concepts
Concept 1
AND is true only when both inputs are true, OR is true when at least one input is true, and NOT inverts a Boolean value.
Exam cue: List all input combinations systematically before evaluating outputs.
Concept 2
Parentheses and operator precedence determine how compound Boolean expressions are evaluated.
Exam cue: Evaluate bracketed or negated subexpressions in separate columns.
Concept 3
A truth table enumerates every input combination and the corresponding output, enabling equivalence and behaviour to be checked.
Exam cue: Translate each real-world condition into a Boolean statement before simplifying.
Risk pitfalls and guardrails
Treating OR as exclusive OR unless the question specifies it.
Guardrail: Do not substitute one board's syntax, protocol list, language version or extension topic for the multi-board core; check the current specification and exam year.
Applying NOT to only one variable when it negates an entire expression.
Guardrail: Do not substitute one board's syntax, protocol list, language version or extension topic for the multi-board core; check the current specification and exam year.
Omitting an input combination from a truth table.
Guardrail: Do not substitute one board's syntax, protocol list, language version or extension topic for the multi-board core; check the current specification and exam year.
Memory anchors
AND
True only when every required operand is true.
OR
True when at least one operand is true.
NOT
Inverts a Boolean value.
Truth table
A table listing an expression's output for every input combination.
Boolean expression
A logical expression whose result is true or false.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
A program uses a Boolean variable named isLoggedIn. Which pair of values can this variable store?
When is `A AND B` true?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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