GCSE Computer Science

This is a book about GCSE Computer Science. The aim is it should be useful as a revision guide or to find alternative explanations to the ones in your textbook.

This book is not the work of a single author. We welcome both students and teachers to improve this book by adding and making changes. Explaining to someone else is one of the best ways to learn.

This book does not teach any specific programming language per se, but rather uses pseudocode and flowcharts to introduce programmng. There are plenty of other wikibooks available which deal adequately with each of the programming languages you might choose to use in studying GCSE Computer Science.

Contents by topic edit

Computer Data Representation edit

Computer Hardware edit

Computer Software edit

Algorithms edit

  • abstraction and decomposition (AQA 3.1.1, Ed 1.2, OCR 2.1)
  • Flowcharts (AQA 3.1.1, CIE 2.1.2,Ed 1.1.1, OCR 2.1)
  • The 3 Basic Constructs: sequence, selection and iteration (AQA 3.2.2, Ed 1.1.2, OCR 2.2)
  • linear search, binary search(AQA 3.1.3, Ed 1.1.8, OCR 2.1)
  • bubble sort, merge sort (AQA 3.1.4, Ed 1.1.8, OCR 2.1)
  • insertion sort (OCR 2.1)
  • trace tables (AQA 3.1.1, CIE 2.1.1, Ed 1.1.5)

Programming edit

Computer Communications edit

  • Internet Security (CIE 1.2.2, Ed 5.2)
  • Encryption (Ed 3.4)

Content by Current Courses edit

You may access the content above of a particular courses by selecting course below (if you are not sure which is your course ask your teacher). These apart from the course introduction below these do not introduce new content but rather connect to the relevant parts of the above content:

Legacy Courses edit

The courses below are not longer taught, but may be of interest some.

How to read the book edit

You will meet several coloured boxes, here are their meanings:

Specification link

What the specification says you must learn for each chapter


Example questions and how to solve them


Questions to test yourself, click below


to check if you were right


Topics that aren't examined but you might be interested in

There will be a lot of concepts that you need to be familiar with, definitions are highlighted like so:

Word - meaning