Compact disc
The compact disc (CD) is a digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then released in October 1982 in Japan and branded as Digital Audio Compact Disc.
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 The readable surface of a compact disc includes a spiral track wound tightly enough to cause light to diffract into a full visible spectrum. | |
| Media type | Optical disc |
|---|---|
| Encoding | Various |
| Capacity | Typically up to 700 MiB (up to 80 minutes audio), 800 MiB (also up to 90 minutes audio), 870 MiB (and up to 99 minutes audio) |
| Read mechanism | 780 nm wavelength, 800 nm wavelength, 870 nm wavelength (infrared and red edge) semiconductor laser (early players used helium–neon lasers),[1] 1,200 Kbit/s (1×) |
| Write mechanism | 780 nm wavelength, 800 nm wavelength, 870 nm wavelength (infrared and red edge) semiconductor laser in recordable formats CD-R and CD-RW, pressed mold (stamper) in read only formats |
| Standard | Rainbow Books |
| Developed by | Philips, Sony |
| Dimensions | Diameter: 120 mm (4.7 in) Thickness: 1.2 mm (0.047 in) |
| Usage | Audio and data storage |
| Extended to | |
| Released |
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| Optical discs |
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The format was later adapted (as CD-ROM) for general-purpose data storage. Several other formats were further derived, including write-once audio and data storage (CD-R), rewritable media (CD-RW), Video CD (VCD), Super Video CD (SVCD), Photo CD, Picture CD, Compact Disc-Interactive (CD-i) and Enhanced Music CD.
Standard CDs have a diameter of 120 millimetres (4.7 in) and are designed to hold up to 74 minutes of uncompressed stereo digital audio or about 650 MiB of data. Capacity is routinely extended to 80 minutes and 700 MiB by arranging data more closely on the same-sized disc. The Mini CD has various diameters ranging from 60 to 80 millimetres (2.4 to 3.1 in); they are sometimes used for CD singles, storing up to 24 minutes of audio, or delivering device drivers.
At the time of the technology's introduction in 1982, a CD could store much more data than a personal computer hard disk drive, which would typically hold 10 MiB. By 2010, hard drives commonly offered as much storage space as a thousand CDs, while their prices had plummeted to commodity levels. In 2004, worldwide sales of audio CDs, CD-ROMs, and CD-Rs reached about 30 billion discs. By 2007, 200 billion CDs had been sold worldwide.[3]