Compact disc

Compact disc
	The readable surface of a compact disc is iridescent because it includes a spiral track wound tightly enough to cause light to diffract into a full visible spectrum.
Media type	Optical disc
Capacity	650‍–‍870 MiB data; 74‍–‍99 minutes audio;
Read mechanism	780 nm laser diode
Write mechanism	780 nm laser diode
Standard	Rainbow Books
Developed by	Philips · Sony
Dimensions	Diameter: 120 mm (4.7 in); Thickness: 1.2 mm (0.047 in);
Usage	Audio storage; Computer data storage;
Extended from	LaserDisc
Extended to	CD-RW; DVD; Super Audio CD;
Released	JP: October 1982; NA/EU: March 1983;

The compact disc (CD) is a digital optical disc data storage format co-developed by Philips and Sony to store and play digital audio recordings. It employs the Compact Disc Digital Audio (CD-DA) standard and was capable of holding of uncompressed stereo audio. First released in Japan in October 1982, the CD was the second optical disc format to reach the market, following the larger LaserDisc (LD). In later years, the technology was adapted for computer data storage as CD-ROM and subsequently expanded into various writable and multimedia formats. As of 2007^[update], over 200 billion CDs (including audio CDs, CD-ROMs, and CD-Rs) had been sold worldwide.

Standard CDs have a diameter of 120 millimetres (4.7 inches) and typically hold up to 74 minutes of audio or approximately 650 MiB (681,574,400 bytes) of data. This was later regularly extended to 80 minutes or 700 MiB (734,003,200 bytes) by reducing the spacing between data tracks, with some discs unofficially reaching up to 99 minutes or 870 MiB (912,261,120 bytes) which falls outside established specifications. Smaller variants, such as the Mini CD, range from 60 to 80 millimetres (2.4 to 3.1 in) in diameter and have been used for CD singles or distributing device drivers and software.

The CD gained widespread popularity in the late 1980s and early 1990s. By 1991, it had surpassed the phonograph record and the cassette tape in sales in the United States, becoming the dominant physical audio format. By 2000, CDs accounted for 92.3% of the U.S. music market share.^[2] The CD is widely regarded as the final dominant format of the album era, before the rise of MP3, digital downloads, and streaming platforms in the mid-2000s led to its decline.^[3]

Beyond audio playback, the compact disc was adapted for general-purpose data storage under the CD-ROM format, which initially offered more capacity than contemporary personal computer hard disk drives. Additional derived formats include write-once discs (CD-R), rewritable media (CD-RW), and multimedia applications such as Video CD (VCD), Super Video CD (SVCD), Photo CD, Picture CD, Compact Disc Interactive (CD-i), Enhanced Music CD, and Super Audio CD (SACD), the latter of which can include a standard CD-DA layer for backward compatibility.

^ "The Compact Disc (CD) is Developed". historyofinformation.com. Retrieved 9 February 2023.
^ "U.S. Music Revenue Database". RIAA. Retrieved 17 March 2024.
^ Lynskey, Dorian (28 May 2015). "How the compact disc lost its shine". The Guardian. Retrieved 17 March 2024.

[1] "The Compact Disc (CD) is Developed". historyofinformation.com. Retrieved 9 February 2023.

[2] "U.S. Music Revenue Database". RIAA. Retrieved 17 March 2024.

[3] Lynskey, Dorian (28 May 2015). "How the compact disc lost its shine". The Guardian. Retrieved 17 March 2024.

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