Abstraction — Problem Solving and Design | IGCSE Computer Science

Exam Frequency Analysis

Past paper frequency (2018 to 2024)

This topic accounts for approximately 6% of your exam marks.

stable

Low

Stable6%

Decomposition, abstraction and structure charts appear as design-focused questions.

Abstraction is the process of removing unnecessary detail from a problem so you can focus on the parts that matter.

A good model of a problem captures the essentials and leaves out the rest. The classic textbook example is the London Underground map: it hides the real geography of London (distances, road layouts, where the river runs) and shows only which stations connect to which lines, because that is the only information a traveller needs.

What to keep, what to throw away

When building a solution, you keep only the data and behaviour the program actually needs:

For a school attendance system, KEEP...	THROW AWAY...
Student name and ID	Hair colour, favourite food, height
Attendance status (present/absent) per day	Mood, weather, lunch choice
Class group	Phone wallpaper

A program that tracks every irrelevant fact would be slower, harder to write and harder to maintain.

Two kinds of abstraction

Data abstraction: choosing which information about a real-world thing to store in the program (e.g. a student record stores name and attendance, not all biological data).
Process abstraction: choosing what a piece of code does without worrying about how it does it (e.g. calculate_percentage(presents, total) hides the multiplication and division behind a clean name).