Compact Disc ( CD) is an optical disc which is used to store digital data. It was initially developed to store sound recordings completely, but later it also permitted the preservation of other types of data. Audio CDs have commercially existed since the time October 1982. In the year 2009, they remain the standard physical storage medium for audio.
Normal CDs have a diameter of 120 mm and can store to 80 minutes of uncompressed audio (700 MB of data). The Mini CD has several diameters ranging from 60 to 80 mm; they are sometimes utilized for CD singles or device drivers, holding up to 24 minutes of audio.
The technology was finally adapted and expanded to encompass data storage CD-ROM, write-once audio and data storage CD-R, , Video Compact Discs (VCD), rewritable media CD-RW , Photo CD, Super Video Compact Discs (SVCD), CD-i, Picture CD and Enhanced CD.