Teach Computing

Revision notes, activities, lesson plans, teaching ideas, and other resources for GCSE, A-Level, and IB Computer Science teachers and students.

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Examples of Local Cryptocurrencies

Digital Money for Local Communities covers three examples of country-wide c...

Hash function A hash function takes arbitrary sized input data (e.g. a fil...

Cryptocurrencies vs regular currencies

What is Bitcoin and How Does it Work? is a high level overview of the Bitco...

Examples of Cryptocurrencies

Bitcoin is by far the most well known cryptocurrency. The Bitcoin website w...

Practice paper 3 exam questions

One of the drawbacks of the yearly case study is that there are no past p...

Emergency Management System Explainer Video

This short video gives an overview of some EMIS features. It includes many ...

Geographic Information Systems (GIS)

For some functionality, an EMIS may also be connected to a GIS (Geographic ...

Programming languages - from Scratch to machine code

The CS Field Guide has a very comprehensive guide to different types of pro...

Assembly language simulators

There are several assembly language simulators available for use online. Si...

Resources discount offer

1.1 Information representation

Click here for recommended Cambridge A-Level Computer Science textbooks.

1.1.1 Number representation

Binary tetris

Binary Tetris

Binary Tetris is a flash game designed to help teach students the binary number system. Players must flip bits to achieve the required number, or add up the bits to calculate the number being represented. I'd recommend asking students to turn their sound off before starting this!

Updated: 2015-04-07
Binary game

Binary Fun

This simple game challenges players to flip the right bits to create the specified number. The current total is displayed as bits are changed, and there is a timer to complete against. Students may be surprised to learn this game was created using Scratch.

Updated: 2017-10-17
Hexadecimal game

Hexadecimal-binary matching game

This is a fun little matching pairs style game in which players must match decimal numbers with their hexadecimal equivalents. A good way of testing students' ability to quickly perform mental conversions. Click here to play.

Updated: 2017-11-05
Introduction to binary

Introducing Binary

The new-look BBC Bitesize site have extensive notes on binary numbers, with clear diagrams and examples of how they work and how they can be added. Several videos brighten up the content and key concepts are related to real-life situations - such as CPU word size. Later pages of the notes cover conversion between different number bases. The site also features short multiple-choice quizes to test students' understanding of the key concepts.

Updated: 2015-04-15
Binary crosswords

Binary crossword activities

These two puzzles are a great way to test students' hexadecimal to binary conversion skills. They work much like a normal crossword, except that the clues are written in hexadecimal and the answers must be written in binary. Once complete, the crosswords make simple bitmap images if the 1s are shaded and the zeroes left blank. You can download puzzle 1 (answers) and puzzle 2 (answers).

These puzzles were created by Gary Kacmarcik at the Computer Science & Engineering for K-12 site - an excellent site which I recommend you visit. They are licensed under the Creative Commons Attribution-Share Alike 3.0 license.

Updated: 2015-04-15
Binary to hexadecimal conversion

Binary to hexadecimal

A worksheet that explains the "divide into groups of 4" method of converting binary numbers to hexadecimal numbers.

This was created by Gary Kacmarcik at the Computer Science & Engineering for K-12 site - an excellent site which I recommend you visit. They are licensed under the Creative Commons Attribution-Share Alike 3.0 license.

Updated: 2015-04-16
Two's Complement

Why we use Two's Complement

This video explains how to represent negative numbers in binary. It explains why we can't use a simple sign bit to represent positive or negative numbers, and then looks at how one's complement solves this problem. Finally it explained how two's complement works and why it is used. Although the beginning of the video goes into a lot of detail, it is useful to understand exactly why two's complement is needed and used.

Updated: 2015-04-29

1.1.2 Images

Image representation

B&W Pixelation

There are three versions of this excellent applet, designed for the University of Chicago's Introduction to Computer Science course to help students understand image representation in computers. In the first version, students simply enter binary digits to represent black or white pixels. In the second version students are introduced to the concept of a very basic file format, with the first two bytes representing the image dimensions. Students can also enter the data in binary or hexadecimal. The final version is even more complex, allowing students to specify the colour depth of the image, and requiring them to enter the appropriate number of bits for each pixel.

Overall this site is an excellent introduction to data storage and image representation, and makes a complex subject quite entertaining.

Updated: 2015-04-09
Bitmap lesson plan

Bitmaps Activity

These activities involve students converting between bitmap images and numeric representations of them in binary and hexadecimal. This is a great way to see how relatively complex information can still be represented as binary. You can download the worksheet with guidance and an additional blank worksheet.

The activities were created by Gary Kacmarcik at the Computer Science & Engineering for K-12 site, which contains an excellent range of activities. They are licensed under the Creative Commons Attribution-Share Alike 3.0 Unported License.

Updated: 2015-04-15

1.1.3 Sound

Computer science sound representation

Lesson - Data representation - sound

This download contains all lesson resources necessary to teach students how sound is represented in binary. It includes PowerPoint presentations, worksheets, and sample sounds for students to play.

This lesson is one of the many excellent resources provided under CC-NC-SA by Mr Colley.

Updated: 2019-03-19

1.1.4 Video

1.1.5 Compression techniques

Image representation

Image Representation - Flash activity

This Flash activity lets students draw a simple bitmap image and represents it using a simple run-length encoding (RLE) algorithm in real time. Students can also important text representations of the compressed data and the application will draw the corresponding image. The web page is not in English but the application is still perfectly usable.

Updated: 2015-04-15
Image, audio, and text compression

Image, audio, and text compression

This very comprehensive page from the Computer Science Field Guide has extensive but clear notes on lossless and lossy compression. The page is well written and designed for a high school audience, with easy to understand examples, video, and even interactive sections. There are also extension "Extra for Experts" sections. The page covers image compression, audio compression, and text compression.

Updated: 2015-04-16
Text and image compression


A short Computerphile video which explains basic compression techniques and how they can be applied to text files and image files. The video also addresses the differences between lossy and lossless compression.

Updated: 2015-05-27

Compression: Crash Course Computer Science

This video explains compression techniques in the context of images. It is recommended that students have an understanding of how image data is stored (e.g. bit depths) before watching this video. The video is very comprehensive and so it may take a couple of viewings to fully understand the details of the examples being presented, but it is worth it.

Updated: 2018-02-17

Lossy and Lossless (RLE) Compression

These videos from Computer Science Tutor make great revision sources. This particular videos covers the theory behind the two types of compression - lossless and lossy.

Updated: 2018-02-17