Compact disc

Compact disc

The readable surface o a Compact disc includes a spiral track wound tightly enough tae cause licht tae diffract intae a full veesible spectrum
Media type	Optical disc
Encodin	Various
Capacity	Typically up tae 700 MiB (up tae 80 minutes audio)
Read mechanism	780 nm wavelength (infrared an reid edge) semiconductor laser, 1200 Kib/s (1×)
Write mechanism	1200 Kib/s (1×)
Developed bi	Philips, Sony
Uisage	Audio an data storage

The compact disc, or CD for short, is an optical disc uised tae store deegital data. The furmat wis oreeginally developed tae store an play back soond recordins anly (CD-DA), but wis later adaptit for storage o data (CD-ROM). Several ither firmats wur further derived frae these, includin write-ance audio an data storage (CD-R), rewritable media (CD-RW), Video Compact Disc (VCD), Super Video Compact Disc (SVCD), Photo CD, PictureCD, CD-i, an Enhanced Muisic CD. Audio CDs an audio CD players hae been commercially available syne October 1982.

Staundart CDs hae a diameter o 120 millimetres (4.7 in) an can hauld up tae 80 minutes o uncompressed audio or 700 MiB (actually aboot 703 MiB or 737 MB) o data. The Mini CD haes various diameters rangin frae 60 tae 80 millimetres (2.4 tae 3.1 in); thay are sometimes uised for CD singles, storin up tae 24 minutes o audio or deliverin device drivers.

At the time o the technology's introduction it haed mair capacity than computer haird drives common at the time. The reverse is now true, wi haird drives far exceedin the capacity o CDs.

In 2004, warldwide sales o CD audio, CD-ROM, an CD-R reached aboot 30 billion discs. Bi 2007, 200 billion CDs haed been sauld warldwide. Compact discs are increasinly bein replaced or supplementit bi ither furms o deegital distribution an storage, such as dounloadin an flash drives, wi audio CD sales droppin nearly 50% frae thair peak in 2000.