Today we went over codes. Codes have been around for a long time. About 2000 years ago there was secret agents who wrote messages on their heads so that when they got back to base they could shave their heads and the message could be read. The key is how the code works, for example, with the word DCHMATQFG meaning EDINBURGH the key is the letter after the one used. You can also use numbers in code. 20 15 27 2 5 27 3 15 14 20 9 14 21 5 4 .