Word games and mathematical puzzles often center around codes and secret messages. But secret messages aren't just for fun and games, they're used all over the world, and in all kinds of circumstances. Governments and military organizations use them to keep secrets, websites use them to keep financial information like credit card numbers and bank account information secret. And everyone enjoys sharing secret messages with friends. There are all kinds of codes you can use to communicate with friends. Some are very complex and difficult to decode, and others are very simple. Some use numbers and mathematics, and others use the alphabet, or pictures and symbols.

Not all codes are designed to keep secrets, though. Can you think of a code which was designed to send messages by telegraph, using sequences of short and long tones called dots and dashes?

Another system of writing looks like a code, but in reality is designed to help people who cannot see. The dots that make up letters are raised from the page so the blind person can feel them with the fingertips. Do you know what that system of writing is called?

Here at The Problem Site's "Codes, Decoding, and Secret Messages" site, you can learn more about a lot of different codes, and even try them out! Just follow the links at the bottom of each page to browse through the unit, or select different encoders to try the various codes.

Some of the codes are complicated, and difficult to understand. Explanations of these codes are broken up into "Basic Exlanations", "Intermediate Explanations", and "Advanced Explanations". You should start at the top of each page and keep reading until you get in over your head. In each case, even if you don't understand the entire explanation, you can probably try out the encoder/decoder!