Designing Algorithms (Cambridge (CIE) O Level Computer Science): Revision Note
Exam code: 2210
What is an algorithm?
Examiner Tips and Tricks
Cambridge IGCSE 0478 assesses your ability to understand, write, and interpret algorithms using pseudocode, flowcharts, and structured design. This page gives examples in the format and style seen in Paper 2, focusing only on examinable methods.
An algorithm is precise set of rules or instructions to solve a specific problem or task
There are three main ways to design an algorithm
Structure diagrams
Flowchart
Pseudocode
Structure Diagrams
What is a structure diagram?
Structure diagrams show hierarchical top-down design in a visual form
Each problem is divided into sub-problems and each sub-problem divided into further sub-problems
At each level the problem is broken down into more detailed tasks that can be implemented using a single subroutine
an example of a structure diagram for a mobile application could be:
Flowcharts
What is a flowchart?
Flowcharts are a visual tool that uses shapes to represent different functions to describe an algorithm
Flowcharts show the data that is input and output, the processes that take place and any decisions or repetition
Lines are used to show the flow of control
Example
Flowchart |
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The casino would like the algorithm refined so that the user also enters their first name and this is used to greet the user when they access the site
Flowchart |
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Pseudocode
What is pseudocode?
Pseudocode is a text-based tool that uses short English words/statements to describe an algorithm
Pseudocode is more structured than writing sentences in English but is very flexible
Example
A casino would like a program that asks users to enter an age, if they are 18 or over they can enter the site, if not then they are given a suitable message
Pseudocode |
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Examiner Tips and Tricks
Pseudocode is not real code—don’t use syntax like print() or input() with brackets. Stick to simple statements like:
INPUT Age
OUTPUT "Welcome"
Adding actual language syntax can lose you marks.
The casino would like the algorithm refined so that the user also enters their first name and this is used to greet the user when they access the site
Pseudocode |
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Examiner Tips and Tricks
If the question asks you to write an algorithm, default to pseudocode. Use flowcharts only when asked or when visual logic helps. Examiners reward clarity, not decoration.
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