1.4 Algorithms
Design, trace, compare and refine algorithms using standard constructs, pseudocode, flowcharts, searching and sorting.
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
Decomposition, abstraction, sequence, selection, iteration and subroutines
Exam cue: Identify the current WJEC unit, the command word and whether the task asks for knowledge, application or computational analysis.
Concept 2
Pseudocode, flowcharts, trace tables and dry runs
Exam cue: Dry-run every branch and loop with representative data, recording variable state and output before judging correctness or efficiency.
Concept 3
Searching, sorting, validation, verification, efficiency and correctness
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
Describing the intended result instead of specifying unambiguous steps, termination conditions and edge-case behaviour.
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
Decomposition
Breaking a complex problem into smaller, manageable subproblems.
Abstraction
Removing irrelevant detail so the essential features of a problem are easier to model.
Selection
Choosing which instructions execute according to a condition.
Iteration
Repeating instructions a fixed number of times or while a condition holds.
Trace table
A table that records variable values and outputs step by step while an algorithm runs.
Validation and verification
Validation tests plausibility against rules; verification checks that data was copied or entered accurately.
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
What is decomposition in computational thinking?
A route planner ignores car colour and passenger names. Which technique is this?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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