A compact disc (or CD) is an optical disc used to store digital data, originally developed for storing digital audio.
A standard compact disc, often known as an audio CD to differentiate it from later variants, stores audio data in a format compliant with the red book standard. An audio CD consists of several stereo tracks stored using 16-bit PCM coding at a sampling rate of 44.1 kHz. Standard compact discs have a diameter of 120mm, though 80mm versions exist in circular and "business-card" forms. The 120mm discs can hold 74 minutes of audio, and versions holding 80 or even 90 minutes have been introduced. The 80mm discs are used as "CD-singles" or novelty "business-card CDs". They hold about 20 minutes of audio.
Compact disc technology was later adapted for use as a data storage device, known as a CD-ROM.
- Compact Disc (CD)
- The compact disc was developed by Sony (Toshitada Doi). Sony first publicly demonstrated an optical digital audio disc in September 1976. In September 1978, they demonstrated an optical digital audio disc with a 150 minute playing time, and with specifications of 44,056 Hz sampling rate, 16-bit linear resolution, cross-interleaved error correction code, that were similar to those of the Compact Disc they introduced in 1982.
- Compact Disc Digital Audio (CD-DA)
- Also called Red Book, CD-DA was the compact disc audio format introduced in 1980 by Sony and Philips.
- The CD-ROM format was developed by Japanese company Denon in 1982. It was an extension of Compact Disc Digital Audio, and adapted the format to hold any form of digital data, with a storage capacity of 553 MiB. CD-ROM was then introduced by Denon and Sony at a Japanese computer show in 1984.