Lesson overview
Represent solutions using ordered steps, structured pseudocode and clear flowchart decisions.
Focus: Algorithms, pseudocode and flowcharts.
What you will learn
- Describe an algorithm as a finite, ordered method.
- Write clear pseudocode using assignment, input, output and decisions.
- Read common flowchart symbols.
- Choose between pseudocode and flowcharts for planning.
Before you start
- Sequence and simple decisions from everyday instructions.
- Basic comparison language such as greater than or equal to.
- Some experience reading simple code is helpful.
Algorithm representation tasks
Use the examples below to move between plain English, pseudocode and flowchart thinking.
Algorithms, pseudocode and flowcharts infographic
Explanation
An algorithm is a precise method for solving a problem. It must have clear steps and should eventually finish.
Pseudocode is structured writing that looks a little like code but does not need to match one programming language exactly. It is useful for showing logic without worrying about syntax.
A flowchart shows the same logic visually. Rectangles usually show processes, parallelograms show input or output, diamonds show decisions and arrows show flow.
Worked examples
Ticket age check
INPUT age
IF age < 16 THEN OUTPUT 'child ticket'
ELSE OUTPUT 'adult ticket'
Answer: This algorithm uses input, selection and output.
Quick checks
1. What does a decision diamond in a flowchart usually represent?
- a. A file size unit
- b. A yes/no or true/false branch
- c. A database table
Reveal answer
Answer: b. Correct. A decision splits the flow based on a condition.
Not quite. Think about branching.
2. Why use pseudocode before coding?
- a. To make the computer faster automatically
- b. To avoid testing
- c. To plan the logic without language syntax getting in the way
Reveal answer
Answer: c. Correct. Pseudocode focuses on logic first.
Not quite. Pseudocode helps plan, but does not replace testing.
Practice
1. Write pseudocode to input a name and output a greeting.
Reveal answer
Answer: INPUT name; OUTPUT 'Hello ' + name.
Marking: Credit input, stored name and output using that name.
2. What flowchart symbol would you use for OUTPUT score?
Reveal answer
Answer: Input/output parallelogram.
Marking: Credit parallelogram or input/output symbol.
3. Give one property of a good algorithm.
Reveal answer
Answer: It is clear, finite, ordered and solves the intended problem.
Marking: Credit any accurate property.
4. Why should a flowchart arrow direction be unambiguous?
Reveal answer
Answer: So the reader can follow the order of execution.
Marking: Credit clear control flow.
Exam practice ladder
- Fluency: recall the key term and use it accurately.
- Application: apply the idea to the scenario rather than giving a generic definition.
- Algorithmic reasoning: show the steps, condition or variable change clearly.
- Evaluation: explain why one method, structure or control is suitable.
Answers and marking guidance
Exact answers and marking guidance are hidden under each question. For this lesson, earn marks by naming the correct Computer Science idea, applying it to the scenario and showing the logic or value change clearly.
Common mistakes
- Writing vague steps such as process data without saying what happens.
- Using a decision without a clear condition.
- Forgetting to output the final result.
- Drawing arrows that make the flow hard to follow.
Extension
Represent the same temperature-checking algorithm as pseudocode and as a flowchart.
Next lesson
Next, continue with Trace Tables and Dry Runs.
Exam-board guidance
Aplailasain is an independent learning resource and is not endorsed by any exam board.
AQA GCSE Computer Science
AQA GCSE Computer Science: this skill supports problem solving, clear algorithms and accurate programming explanations.
OCR GCSE Computer Science
OCR GCSE Computer Science: expect precise algorithm reasoning, trace work and careful use of programming vocabulary.
Pearson Edexcel GCSE Computer Science
Pearson Edexcel GCSE Computer Science: practise explaining the method as well as giving the final answer or code.
Eduqas GCSE Computer Science
Eduqas GCSE Computer Science: secure the transferable idea first, then check how your class applies it in tasks.
WJEC Wales
WJEC Wales: use accurate terminology and show enough working for the examiner to follow your logic.
CCEA
CCEA: connect the idea to your class route and use the same algorithm, programming or systems vocabulary your teacher uses.