In the first lesson we learnt about semaphore, which is a kind of code used to send messages from ship to ship across the sea. It uses flags held in various positions and each position stands for a letter of the alphabet. Our class practised sending codes to one another using the flags. It was tricky!

The next week, we looked at Morse code. It consists of a series of dots or dashes, transmitted using either sound or light. We used torches to send messages to each other – a quick flash for a ‘dot’ and a long beam of light for a ‘dash’. Although it was still difficult to decode, most of us thought it was a little easier than semaphore to use. We learnt that on/off electrical signals form the basis of communication and internet routers pass on data packets in a similar way, so these codes are helping us understand how the Internet works.

This week, we used the Caesar cipher to create our own codes. Each letter of the message was shifted one place along in the alphabet, for example ‘B’ stands for ‘A’, and ‘C’ stands for ‘B’ and so on. ‘Hello’ is written as IFMMP. It was really fun writing codes to each other!

Try it yourself: www.simonsingh.net/The_Black_Chamber/caesar.html