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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3.2 Data Representation

Lesson resources

Computer Science crosswords pack
Computer Science crosswords pack
Data representation lesson activity
Spot the mistakes activity
Data representation game
Data representation revision game
Recommended IGCSE Computer Science textbooks
IGCSE Computer Science textbooks

3.2.1 Understand how computers encode characters


Characters, Symbols and the Unicode Miracle

Characters, Symbols and the Unicode Miracle explains how ASCII arose from the need to communicate data in a compatible manner between computer systems, and the problems that arise with this apparently simple task. It then discusses the creation of the Unicode system.

Updated: 2015-04-29
Unicode character table

Unicode Table

Unicode table is a nice scrollable web page which lists all of the unicode characters. The title and a brief description of each section is presented while you scroll. This page is useful for helping students realise just how many different characters need to be represented by computer systems, and the problems this would cause with a standard like Unicode.

Updated: 2015-04-29
Lesson - text representation

Lesson - Data representation - text

This download contains all lesson resources necessary to teach students how ASCII is used to representation text in a computer system. The download includes several fun activities where students have to uncover 'secret' messages using their understanding of binary and ASCII. There are different worksheets for students of different levels.

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

Updated: 2017-10-15
Text representation worksheet

Text representation worksheets

Gary Kacmarcik at the excellent cse4k12 site has created a set of sheets for a lesson activity on text representation. The first sheet is an ASCII table and the other two sheets ask students to encode a text message and decode a message respectively. Note that students are expected to encode and decode using hexadecimal rather than binary (although they could easily be asked to use binary instead).

Updated: 2017-10-17
Image representation

CS Field Guide - Data representation

CS Field Guide is an absolutely fantastic resource filled with material that is well written, clear,and accessible. Each section comes with highlighted key points, extension points, and even interactives to help understand the concepts. The interactives are excellent as teaching resources (many of them are linked here), while the notes themselves make excellent revision resources - particularly for GCSE.

This section covers all aspects of data representation - numbers, text, images, and instructions.

Updated: 2017-10-24
Spot the mistakes classroom activity

Spot the mistakes exercises

The slides in this presentation present basic 'facts' about computing fundamentals: input, output, binary, hexadecimal, and data representation. Each slide contains a number of basic mistakes (highlighted on the following slide). Students simply need to read through the text, spot the mistakes - and correct them. These activities work well as quick lesson starters or plenaries to check understanding.

Updated: 2017-10-24
ASCII and Unicode

Representing Text in Binary

This video clearly explains the two main ways of representing text in binary - ASCII and Unicode, plus the advantages and disadvantages of each. The limitations of ASCII, which led to the development of Unicode, are also clearly explained.

Updated: 2018-12-08

3.2.2 Understand how bitmap images are represented

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
Hexadecimal colour codes

Hexadecimal colour codes

Section 5.5.2 of this much bigger page on data representation covers the uses of hexadecimal numbers to represent colours in images. It explains the correlation between the hexadecimal digits and the number of bits available, and the effect the bit depth has on the appearance of the image. The excellent interactives really make the concept come alive and visually highlight these differences to students. A highly recommended resource.

Updated: 2015-06-03
Pixel viewer

Pixel colour code viewer

This pixel viewer can help students understand how images are created and represented. Zooming right into the image reveals the RGB values of each pixel, shown in decimal.

Updated: 2017-10-24
Bit comparer

Image bit depth comparison

This is a great little resource for demonstrating the effect of bit depth on images. The same image is displayed at various colour depths from 24 bit to 2 bit. It is also possible to upload your own images and have them displayed in the same way.

Updated: 2017-10-24
RGB Colour matcher

RGB Colour matcher

A colour matching tool that asks users to play with the RGB sliders to match a specified colour. This is a great way to help students understand how red, green, and blue are mixed to produce colours. What makes this colour matcher stand out is that it also represents the colour values in binary (24 bit) at the bottom. This makes it a useful companion for tools like Pixelization (see elsewhere on this page).

Updated: 2017-10-24

3.2.3 Understand how analogue data is represented in binary

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

3.2.4 Understand the limitations of binary representation of data