The path followed by the head over the surface of a recording medium (usually magnetic or optical). The tracks on magnetic disks are circular and concentric. On optical disks they may be similar but are more often turns of a continuous spiral path. Most magnetic tapes carry several tracks running the length of the tape; these may be written or read simultaneously (parallel recording) or, for other tape formats, one at a time (serial recording, or serpentine recording if alternate tracks are recorded in opposite directions). In helical scan recording the tracks run diagonally across the axis of the tape.
On CD-ROM optical disk, the word track is also used (as it is on compact audio disk) to define an item of the contents, of variable length, which may occupy many turns of the spiral path.