CD Rom is short for Compact Disk Read only memory. It is a data storage device which can store much more information than a floppy disk - 650Mb as opposed to 1.44 Mb - but at present this data has to be written on to it by a special machine rather than an ordinary computer. "Read only memory" means that once stored on the disk, the information cannot be changed.

CD Roms are made of plastic and data is stored in binary form as holes etched on to the surface which are then read by a laser when the CD Rom is "played" in the computer's "CD Rom drive" (in the same way that audio CDs are played in hi-fi systems). CDs will are now being developed that users can write on to as well as read.

See also Collin, S.M.H. [ed.], Dictionary of Multimedia, Peter Collin Publishing, Teddington, Middlesex, 1995, p42.

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