Digital media is simply composed of a discrete binary code which can contain data (material to be operated upon) and program (the directions for operations on data). Such media can be recorded and accessed by many means; magnetic (discs, tape), optical (CD, CD-ROM), paper (paper tape or cards in the early days of computing).

A music CD contains only data, which can be played by a CD player. A CD-ROM contains both data and programs which can alter that data. A feature of programmable (and self-reprogrammable) media is that it allows varying levels of interaction between a reader and the material itself.