Compact disc is a round, flat platter on which recorded music, computer data, or other information is stored in the form of digital (numerical) code. The main use of compact discs (CD's) is to store recorded stereophonic music. Discs used for this purpose, called Audio CD's, are played on a CD player. The other major type of CD is called CD-ROM (Compact Disc Read-Only Memory). CD-ROM's can store files of text, pictures, sound, and other data, as well as video game programs and other software. These discs are played on a computer's CD-ROM drive or on a special CD-ROM player. Other types of CD's can store high-quality images or motion pictures.
CD's are made of hard plastic coated with thin metal, usually aluminum. CD's have only one playing side. A standard CD measures about 4 3/4 inches (120 millimeters) in diameter, with a 1/2-inch (15-millimeter) center hole.
