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 and branded as Digital Audio Compact Disc.

Compact disc
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 typeOptical disc
EncodingVarious
CapacityTypically up to 700 MB (up to 80 minutes' audio)
Read mechanism780 nm wavelength (infrared and red edge) semiconductor laser (early players used helium–neon lasers),[1] 1,200 Kbit/s (1×)
Write mechanism780 nm wavelength (infrared and red edge) semiconductor laser in recordable formats CD-R and CD-RW, pressed mold (stamper) in read only formats
StandardRainbow Books
Developed byPhilips, Sony
UsageAudio and data storage
Extended toCD-RW
DVD
Super Audio CD
ReleasedOctober 1982; 38 years ago (1982-10) (Japan)
March 1983; 38 years ago (1983-03) (Europe and North America)

The format was later adapted for storage of data (CD-ROM). Several other formats were further derived from these, 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 MB of data. Capacity is routinely extended to 80 minutes and 700 MB by arranging more data 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 MB. By 2010, hard drives commonly offered as much storage space as a thousand CDs, while their prices had plummeted to commodity level. 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.[2]