Compact disc

A 120-millimeter optical disc that stores digital data as microscopic pits and lands read by a laser. Compact discs became a standard medium for recorded music and computer files.

Pit and land: A microscopic depression or flat region in an optical disc’s data layer, detected through changes in reflected laser light. Their transitions encode the signal on a compact disc.
Sony: A Japanese electronics and entertainment company founded in 1946. Sony developed the compact-disc audio format with Philips.
Optical disc: A data-storage medium read or written using focused light. The compact disc is one member of this broader storage family.
CD-ROM: A read-only compact-disc format for distributing computer data and software. It adapted the disc for general digital files rather than audio alone.
Vinyl record: An analog sound-storage medium in which a stylus follows a modulated groove on a rotating disc. It was the dominant music format that compact discs challenged.
Eight-to-fourteen modulation: A coding scheme that maps each eight-bit data byte to a fourteen-bit pattern with controlled transition spacing. It shapes compact-disc bit patterns for reliable optical reading.
Philips: A Dutch technology company founded in 1891, known for consumer electronics and healthcare technology. Philips collaborated with Sony on the disc’s design and standards.
Digital audio: Sound represented as numerical samples rather than as a continuously varying physical signal. Compact-disc audio stores sound in this digital form.
CD-R: A recordable compact disc whose data layer can be written once by a compatible drive. It made compact discs useful for personal recording and file storage.
Compact cassette: A magnetic-tape format in a plastic cassette, used for recording and playing audio. Its portability and recordability contrasted with the compact disc’s optical playback.

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