GCSE Computer Science: Algorithms Revision

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What does a binary search need to work?

Algorithms is a core part of GCSE Computer Science. Revise the key concepts and common mistakes below, then lock them in with the free games.

Key concepts

AlgorithmA precise step-by-step method for solving a problem.

Pseudocode & flowchartsWays to express an algorithm before coding.

SearchingLinear search (any list) and binary search (sorted list).

SortingOrdering data, e.g. bubble, merge and insertion sort.

DecompositionBreaking a problem into smaller parts.

AbstractionHiding unnecessary detail to focus on what matters.

Best caseFastest possible scenario for the algorithm.

Worst caseSlowest possible scenario for the algorithm.

ComparisonChecking which of two items is bigger.

SwapExchange two items' positions.

What your exam board covers

Where Algorithms sits in each exam board's specification. Tap a board to see what it lists.

AQAFundamentals of algorithmsSpec 8525

Representing algorithms
Efficiency of algorithms
Searching algorithms
Sorting algorithms

Source: AQA GCSE Computer Science (8525) specification — Subject content, accessed 23 June 2026.

OCRAlgorithmsSpec J277

Part of: Component 2 — Computational thinking, algorithms and programming

Source: OCR GCSE (9–1) Computer Science (J277) specification, accessed 23 June 2026.

Learn Algorithms step by step

Free interactive mini-lessons: short screens, worked examples and quick checks. Pick your exam board:

Other boards:Edexcel Cambridge IGCSE

Common mistakes to avoid

Questions where students often pick the tempting wrong answer — make sure you know the right one:

What does a binary search need to work?✗ It works on any unsorted list. ✓ A sorted list.

Must an algorithm be written in code?✗ Yes, an algorithm has to be program code. ✓ No — it's a step-by-step method (e.g. pseudocode or a flowchart).

Is an algorithm the same thing as a computer program?✗ Yes - algorithm is just the formal word for program code. ✓ No - an algorithm is the abstract sequence of steps; a program is one implementation of it in a particular language. The same algorithm can be coded many ways.

Which best defines an algorithm?✗ Any piece of computer hardware ✓ A precise sequence of steps that solves a problem

Are abstraction and decomposition the same thing?✗ Yes - both just mean simplifying a problem, so they are identical. ✓ No - decomposition splits a problem into smaller parts, while abstraction removes irrelevant detail from the problem; they are separate, complementary techniques.

Practise Algorithms — free games

Test yourself with these quick revision games for this topic:

▶ Two Truths, One Lie ▶ Reveal Race ▶ Connections Grid ▶ Falling Words ▶ Word Web

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Algorithms

Key concepts

What your exam board covers

Common mistakes to avoid

Practise Algorithms — free games

More GCSE Computer Science topics