A Compact Disc or CD is an optical disc used to store digital data, originally developed for storing digital audio. The CD, available on the market since late 1982, remains the standard playback medium for commercial audio recordings to the present day, although it has lost ground in recent years to MP3 players, which have greater storage capability (albeit with lower sound quality).
An audio CD consists of one or more stereo tracks stored using 16-bit PCM coding at a sampling rate of 44.1 kHz. Standard CDs have a diameter of 120 mm and can hold approximately 80 minutes of audio. There are also 80 mm discs, sometimes used for CD singles, which hold approximately 20 minutes of audio. The 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 respectively). CD-ROMs and CD-Rs remain widely used technologies in the computer industry as of 2007. The CD and its extensions have been extremely successful: in 2004, the worldwide sales of CD audio, CD-ROM, and CD-R reached about 30 billion discs. By 2007, 200 billion CDs had been sold worldwide.
In 1979, Philips and Sony set up a joint task force of engineers to design a new digital audio disc. The task force, led by prominent members Kees Immink and Toshitada Doi, progressed the research into laser technology and optical discs that had been started by Philips in 1977. 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 video LaserDisc technology. Philips also contributed Eight-to-Fourteen Modulation (EFM), which offers both a long playing time and a high resilience against disc defects 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 first Compact Disc for commercial release rolled off the assembly line on August 17, 1982, at a Philips factory in Langenhagen, near Hanover, Germany. The first title released was ABBA‘s The Visitors (1981). CDs and the CD player CDP-101 reached the market on October 1, 1982 in Japan, and early the following year in the United States and other markets. 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 first artist to sell a million copies on CD was Dire Straits, with their 1985 album Brothers in Arms.
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 generalising 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.