Type of computer storage medium that is read optically (e.g., by a laser). A CD-ROM drive uses a low-power laser beam to read digitized (binary) data that have been encoded onto an optical disc in the form of tiny pits, then feeds the data to a computer for processing. Because it uses digital data, a CD-ROM can store images and sound in addition to text and is thus used in video and audio devices to store music, graphics, and movies (see compact disc). Unlike conventional magnetic-storage technologies (e.g., hard disks), CD-ROM drives cannot write information (that is, accept the input of new data), hence the tag “read-only.” Recordable compact discs (called CD-R) must be written on a CD-R recorder and can be played on any CD-ROM drive.

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