The reliable storage of data for later use and the reliable transmission of data from one place to another are central to information technology. Whilst they would appear to be different tasks, they actually have a great deal in common. Digital transmission consists of converting data into a waveform suitable for the path along which it is to be sent. Digital recording is basically the process of recording a digital transmission waveform on a suitable medium. In this chapter the fundamentals of digital recording and transmission are introduced along with descriptions of the coding and error-correction techniques used in practical applications.