Revision notes, activities, lesson plans, teaching ideas, and other resources for GCSE, A-Level, and IB Computer Science teachers and students.
Examples of Local Cryptocurrencies
Digital Money for Local Communities covers three examples of country-wide c...
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...
C3 Distributed Approaches to the Web
These are teaching and learning resources for the IB Computer Science course C: Web science, which is an optional unit.
Click here for recommended IB Computer Science textbooks.
C.3.6 Lossy and Lossless 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.
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.
Run Length Compression (RLE) interactive
This activity shows how a computer would represent a simple image when using Run Length Compression (RLE). Students can alter the image to see how the compression data would change. This is a good resource for helping students understand how lossless compression does not always result in significant size reduction.
JPEG Compression comparison
A simple interactive that compares a highly compressed JPEG image with a less compressed image. A slide lets you view different parts of the image. JPEG banding is particularly visible in the sky but less so in other areas - the reasons for this make for interesting classroom discussions.
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.
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.