Teach Computing

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

What's New

UK Computing Laws

This video from Computer Science Tutor covers the main UK computing laws re...

Wireless Networking (Wi-Fi, Security, and Hardware)

This video about wireless networking includes everything that is needed for...

Network topology videos

These four excellent videos from Computer Science tutor cover the four ma...

Network protocols

These four videos explain the main networking protocols that students are l...

Embedded Systems video

This short video is a good over of embedded systems, covering the main poin...

Representing Text in Binary

This video clearly explains the two main ways of representing text in binar...

Types of Malware

This video explains the various types of malware including viruses and troj...

Protecting against Malware

Following on from the Types of Malware video, this video explains technique...

Video: Network Security #1

This video gives an overview of the threats to networked computer systems, ...

Resources discount offer

Binary Number System

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

Unsigned binary

Binary to decimal

Binary-Decimal Conversions

This video contains lots of examples of converting binary numbers to decimal numbers, and vice versa. A good revision guide.


Updated: 2018-02-17

Unsigned binary arithmetic

Binary addition

Binary Addition & Overflow

Another excellent video from ComputerPhile with their usual clear explanations and worked examples. This video recaps binary numbers and then explains how to perform binary addition. It also deals with the potential problem of overflow and how it can be handled.


Updated: 2015-04-29

Signed binary using two’s complement

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

Numbers with a fractional part

AQA A Level computer science

A-Level appendix unit - PG Online

Floating point numbers, adders, D-type flip flops are covered in this free lesson resource unit from PG Online. The presentations and activities are designed for the AQA AS and A-Level courses, but the content is relevant to other A-Level courses too.


Updated: 2017-10-17

A-Level only content

Rounding errors

Absolute and relative errors

Range and precision

Normalisation of floating point form

Underflow and overflow