Coding theory is an approach to various science disciplines -- such as information theory, electrical engineering, digital communication, mathematics, and computer science -- which helps design efficient and reliable data transmission methods so that redundancy can be removed and errors corrected.

It also deals with the properties of codes and with their fitness for a specific application.

There are three classes of codes

1. Source coding (Data compression)
2. Channel coding (Forward error correction)
3. Joint source and channel coding.

The first, source encoding, attempts to compress the data from a source in order to transmit it more efficiently. This practice is found every day on the Internet where the common "Zip" data compression is used to reduce the network load and make files smaller. The second, channel encoding, adds extra data bits to make the transmission of data more robust to disturbances present on the transmission channel. The ordinary user may not be aware of many applications using channel coding. A typical music CD uses the Reed-Solomon code to correct for scratches and dust. In this application the transmission channel is the CD itself. Cell phones also use coding techniques to correct for the fading and noise of high frequency radio transmission. Data modems, telephone transmissions, and NASA all employ channel coding techniques to get the bits through, for example the turbo code and LDPC codes.