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.

Compact disc
OD Compact disc.svg
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 teepOptical disc
EncodinVarious
CapacityTypically up tae 700
MiB (up tae 80 minutes audio)
Read mechanism780 nm wavelength
(infrared an reid edge)
semiconductor laser, 1200 Kib/s (1×)
Write mechanism1200 Kib/s (1×)
Developed biPhilips, Sony
UisageAudio an data storage

Staundart CDs hae a diameter o 120 millimetre (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 millimetre (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.[1] 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.[2]

ReferencesEedit

  1. "Compact Disc Hits 25th birthday". BBC News. 17 August 2007. Retrieved 1 December 2009.
  2. Plambeck, Joseph (30 Mey 2010). "As CD Sales Wane, Music Retailers Diversify". The New York Times.