In
computing, an
optical disk is a flat, circular, plastic disk coated with material on which bits may be stored in the form of highly reflective areas and significantly less reflective areas, from which the stored
data may be read when illuminated with a narrow-
beam source, such as a
laser diode.
Usual optical disks include:
Note: The bits are stored sequentially on a continuous spiral track.
Source: from Federal Standard 1037C