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What is an algorithm?
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At KS3 you met algorithms as sets of instructions. GCSE Computer Science expects you to read, follow and write them precisely.
Algorithms
An algorithm is a precise, step-by-step set of instructions for solving a problem or completing a task.
A good algorithm is unambiguous (each step has one meaning), the steps are in the right order, and it finishes.
A recipe and the directions to a friend's house are everyday algorithms. A program is an algorithm written in a programming language.
A good algorithm is unambiguous (each step has one meaning), the steps are in the right order, and it finishes.
A recipe and the directions to a friend's house are everyday algorithms. A program is an algorithm written in a programming language.
Ways to show an algorithm
You can show the same algorithm as:
Written description: numbered steps in plain English.
Flowchart: shapes joined by arrows.
Pseudocode: structured, code-like English that is not tied to one language.
Program code: for example Python, which a computer can run.
Written description: numbered steps in plain English.
Flowchart: shapes joined by arrows.
Pseudocode: structured, code-like English that is not tied to one language.
Program code: for example Python, which a computer can run.
Flowchart symbols
Learn these five. They come up again and again.
Follow this algorithm with the number 7.
1. Take a number.
2. Double it.
3. Add 4.
4. Halve the result.
5. Output the answer.
- Double 7: 7 × 2 = 14
- Add 4: 14 + 4 = 18
- Halve: 18 ÷ 2 = 9
Answer: 9
An algorithm is a precise, ordered set of steps that finishes. It can be shown as a written description, a flowchart, pseudocode or code. Flowcharts: rounded rectangle start/stop, rectangle process, diamond decision, parallelogram input/output.
The interactive lesson includes the diagrams for this topic.
Check you have got it
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