1.6 Logical Operations
Construct, interpret and apply Boolean expressions, logic gates and truth tables.
How to study WJEC GCSE Computer Science
Learn the computing principle, apply it to the named system or scenario, trace the data and control flow, and test the result against requirements.
Core concepts
Concept 1
Boolean values, relational conditions and compound expressions
Exam cue: Identify the current WJEC unit, the command word and whether the task asks for knowledge, application or computational analysis.
Concept 2
AND, OR, NOT and XOR gates and truth tables
Exam cue: Evaluate inner expressions first, record every input combination and check that the final output matches the stated rule.
Concept 3
Combining logical operations in programs and control systems
Exam cue: Use precise terminology, trace inputs and state changes, and test the answer against the data, scenario or program behaviour.
Risk pitfalls and guardrails
Treating OR as exclusive OR, or failing to apply NOT to the correct input or grouped expression.
Guardrail: Avoid generic descriptions, unchecked traces and cross-board assumptions; make every answer depend on the named data, system, algorithm or scenario.
Importing the legacy WJEC structure, a different board's content or a Foundation/Higher tier assumption.
Guardrail: Use qualification code 3460QS or 3460CS and the current two-unit untiered structure; do not import a legacy or cross-board route.
Giving a generic description without applying it to the named system, data set, algorithm or pre-release scenario.
Guardrail: Practice cannot replace the annual live brief, specified Python environment, clean-copy rule, restricted examination files or Surpass upload process.
Memory anchors
AND
True only when every input is true.
OR
True when at least one input is true.
NOT
Inverts a Boolean value.
XOR
True when the inputs are different.
Truth table
A table listing every input combination and the resulting output of a logical expression or circuit.
Precedence
Brackets make evaluation order explicit and prevent ambiguity in compound logical expressions.
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
An alarm output uses the Boolean expression A AND B. Under which input state will the output be true?
When is `A OR B` false?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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