That Blue Square Thing

AQA Computer Science GCSE

July 2019: the AQA CompSci area is almost complete. Most of the content for units 3-6 is now up and there's quite a lot of Unit 7 material. There's still some work to do, particularly on Paper 1 units, but it's getting there.

Data Representation - Revision

This unit appears on both exam papers.

This means that there will be some knowledge based questions, but also plenty of questions where you have to do simple calculations or know how to work something else. Although you need to learn definitions, it's more important to be able to use the knowledge in a practical way.

It looks as if there aren't many marks from this unit on paper 1. Questions on that paper are likely to focus on the ways in which bitmap images are encoded and how this data can be used in programming. There may also be some simple binary or a need to deal with conversions between Bytes, kilobytes, megabytes etc... There's a chance that Run Length Encoding might come up on paper 1 as well.

Paper 2 will have questions on binary and converting between file sizes (Bytes, MB etc...) for sure and then there will be marks on the other sections of the syllabus as well. Quite a lot of the marks for paper 2 are quite straightforward questions from this unit and its worth making sure you can deal with anything that gets thrown at you.

Revision materials

PDF iconSyllabus content - a slightly edited version of the syllabus document showing what you need to know in some detail

PDF iconKey definitions, knowledge and skills - a summary of the things you need to learn all on one slide

There is a separate set of slides on compression revision.

PDF iconCompression - a summary

There's also an online quiz on the first part of the unit - binary, hex and decimal numbers.

Test iconBinary, hexadecimal and decimal numbers quiz


It's useful to work through sample questions for the skills elements of this unit. You'll find the basics and some questions on each of the pages, but here's four pages of sample questions dealing with everything from binary to image and sound representation - primarily involving lots of calculations.

Remember, Computer Science is a none calculator subject. You have to do the maths by hand.

PDF iconRevision Questions - you might want to print this


I'll also give you the answers. But try to resist the temptation to cheat. Do the questions, then check the answers. Preparation works better that way round - trust me.

PDF iconThe answers

If I've made a mistake with any of the answers let me know! I did double check them (and found two errors - one of which was a simple maths error - so really do do that thing you teachers say and check your answers too...)

Worked Answers

And I went through and showed my working by hand as well. This has the advantage that you can see exactly how I did the questions - the working out that I used. By looking back at the teaching pages (on the left) you should find the same methods there.

PDF iconWorked answers

You'll see that I've made clear what the answer is where necessary (by crossing my working out through on question 2, for example) and that I've tended to include units even when they aren't necessary.

Also notice that b is the official abbreviation for bits and B for Bytes. These are in the syllabus, so I can use them without needing to write the long form - and I've done that at times.