That Blue Square Thing

AQA Computer Science GCSE

This page is up to date for the new AQA 8525 syllabus for the 2022 exam.

Data Representation - Binary Numbers

Computers are, at their heart, very complex machines which use a very simple way of storing information. It all comes down to Binary numbers - 1s and 0s.

PDF iconHow computers deal with numbers

PDF iconBinary Numbers - binary and denary - an introduction

Converting Binary to Decimal and Back Again

You need to be able to convert from binary to denary.

PDF iconBinary Numbers - converting from binary to decimal method - how to do it

PDF iconBinary Numbers - converting from binary to decimal questions

And you need to be able to convert from denary to binary as well. Which is a little harder.

PDF iconBinary Numbers - converting from decimal to binary method - how to do it

PDF iconBinary Numbers - converting from decimal to binary questions

Binary numbers: largest, how many and range

The exam board likes to ask questions like:

These are actually really easy questions, but you need to know what to do - it's really easy to get confused.

These guides make answering this sort of questions a piece of cake.

PDF iconFinding the largest binary number in X bits

PDF iconFinding the number of binary numbers in X bits

PDF iconFinding the range of binary numbers in X bits

Why Binary?

Absolutely everything that a computer does can only be stored using binary numbers. Every single thing has to be able to be reduced down to a series of 1s and 0s to get it inside a computer of any kind.

Just think of what that means:

The reason for all this is that computers just can't deal with anything else. A switch can only be on or off - it can be a 1 or a 0. Nothing else.

PDF iconWhy Binary? - some theory which reminds you why we need to use binary.

PDF iconMore Complex Why Binary? - this details some of the ways in which data storage has developed over time and some other ways in which data can be stored and transferred using alternatives to switches.

Number Bases - a Summary

The slides summarise how the three numbers bases (binary, decimal and hexadcimal) work. This is probably best left until you know about all of them and might be helpful for revision.

PDF iconNumber Bases Summary

Binary Revision Questions

Some sets of revision questions, dealing with all of the binary stuff, for when you need them:

PDF iconBinary Revision Questions 1 - everything binary only

PDF iconBinary Revision Questions 2 - binary and hex

Here are some summary questions that you can do at this stage.

PDF iconBasic Binary Questions

PDF iconBinary Questions from class