What is computational thinking, and how are algorithms expressed using flowcharts and pseudocode?
Computational thinking through decomposition and abstraction, what an algorithm is, and expressing algorithms using flowcharts and pseudocode.
A focused answer to the WJEC GCSE Computer Science Unit 1 content on computational thinking and algorithms, covering decomposition and abstraction, what an algorithm is, and how algorithms are expressed using flowcharts (with the standard symbols) and pseudocode, with worked examples.
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What this topic is asking
WJEC wants you to know what computational thinking is (decomposition and abstraction), what an algorithm is, and how algorithms are expressed using flowcharts and pseudocode. This is part of the Algorithms and programming principles content in Unit 1 of WJEC GCSE Computer Science (3500).
Computational thinking: decomposition and abstraction
What an algorithm is
Flowcharts
Pseudocode
Try this
Q1. State what decomposition means. [1 mark]
- Cue. Breaking a large, complex problem down into smaller, more manageable sub-problems.
Q2. Name the flowchart symbol used for a decision. [1 mark]
- Cue. A diamond.
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC-style Unit 14 marksExplain what is meant by decomposition and abstraction in computational thinking, giving an example of each.Show worked answer →
A Unit 1 computational-thinking question. Decomposition means breaking a large, complex problem down into smaller, more manageable sub-problems that can be solved one at a time (1 mark), for example splitting "write a game" into handling input, updating the score and drawing the screen (1 mark). Abstraction means removing or hiding unnecessary detail so you can focus on the important parts of a problem (1 mark), for example a map of a town shows the roads but leaves out individual buildings and trees (1 mark). Markers reward breaking down for decomposition and hiding detail for abstraction, each with a sensible example. A common error is to swap the two, or to describe abstraction as making something shorter rather than removing detail.
WJEC-style Unit 13 marksState what an algorithm is and name two ways an algorithm can be expressed.Show worked answer →
A Unit 1 algorithms question. An algorithm is a step-by-step sequence of instructions to solve a problem or carry out a task (1 mark). Two common ways to express an algorithm are a flowchart (a diagram using standard symbols connected by arrows) and pseudocode (structured, English-like statements that resemble code without being a specific language) (1 mark each, up to 2). Markers reward the step-by-step definition and any two valid representations (flowchart, pseudocode, written description, code). A common error is to confuse an algorithm with a program; the algorithm is the plan, and the program is its implementation in a language.
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