CDs

A Compact Disc (CD) is an optical disc used to store digital data, originally developed for storing digital audio. The CD, available on the market in late 1982, remains the standard physical medium for commercial audio recordings as of 2006. more...

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An audio compact disc consists of one or more stereo tracks stored using 16-bit PCM coding at a sampling rate of 44.1 kHz. Standard compact discs have a diameter of 120 mm or 80 mm. The 120 mm discs can hold approximately 80 minutes of audio. The 80 mm discs, sometimes used for CD singles, hold approximately 20 minutes of audio. Compact disc technology was later adapted for use as a data storage device, known as a CD-ROM, and to include record-once and re-writable media (CD-R and CD-RW). CD-ROMs and CD-Rs remain widely used technologies in the personal-computer industry as of 2006. The CD and its extensions have been extremely successful: in 2004, the annual worldwide sales of CD-Audio, CD-ROM, and CD-R reached about 30 billion discs.

History

In 1979 Philips and Sony decided to join forces, setting up a joint task force of engineers whose mission was to design the new digital audio disc. Prominent members of the task force were Kees Immink and Toshitada Doi. After a year of experimentation and discussion, the taskforce produced the "Red Book," the Compact Disc standard. Philips contributed the general manufacturing process, based on the video LaserDisc technology. Philips also contributed the Eight-to-Fourteen Modulation, EFM, which offers both a long playing time and a high resilience against disc handling damage such as scratches and fingerprints; while Sony contributed the error-correction method, CIRC. The Compact Disc Story, told by a former member of the taskforce, gives background information on the many technical decisions made, including the choice of the sampling frequency, playing time, and disc diameter. According to Philips, the Compact Disc was thus "invented collectively by a large group of people working as a team."

The Compact Disc reached the market in late 1982 in Asia and early the following year in other markets; for example, it was released in the United States in March, with the first CDs available being 16 Japanese-made titles from CBS/Sony. This event is often seen as the "Big Bang" of the digital audio revolution. The new audio disc was enthusiastically received, especially in the early-adopting classical music and audiophile communities and its handling quality received particular praise. As the price of players sank rapidly, the CD began to gain popularity in the larger popular and rock music markets.

The design of the CD was originally thought of as an evolution of the gramophone record, rather than primarily as a data storage medium. Only later did the concept of an 'audio file' arise, and the generalizing of this to any data file. From its origins as a music format, Compact Disc has grown to encompass other applications. In June 1985, the CD-ROM (read-only memory) and, in 1990, CD-Recordable were introduced, also developed by Sony and Philips.

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