Theoretical computer science
Information theory talks about the notion of information. Originally it was developed for signal processing. It is concerned with how a message needs to be changed, so that it can be transmitted over a  channel, an how to undo the changes at the other end, so that the original message can be recovered. These processes are known as encoding and decoding. Information theory also talks about how much self-information there is in a message. This is the theoretical basis for data compression, cryptography and digital signatures. Error detection and correction is about detecting if errors have occurred when the message was transmitted. In some cases, it may be possible to recover the original message even if errors have occurred, or part of the message has been lost.