Compact Disc (Cd)

Molded plastic disc containing digital data that is scanned by a laser beam for the reproduction of recorded sound or other information. Since its commercial introduction in 1982, the audio CD has become the dominant format for high-fidelity recorded music. Digital audio data can be converted to analog form to reproduce the original audio signal (&see; digital-to-analog conversion).

Coinvented by Philips Electronics and Sony Corp. in 1980, the compact disc has expanded beyond audio recordings into other storage-and-distribution uses, notably for computers (CD-ROM) and entertainment systems (videodisc and DVD). An audio CD can store just over an hour of music. A CD-ROM can contain up to 680 megabytes of computer data. A DVD, the same size as traditional CDs, is able to store up to 17 gigabytes of data, such as high-definition digital video files.