CD – Compact Disk. This is an optical disc format developed by Philips and Sony to store and play digital audio recordings. The first CD was manufactured in 1982. Standard CDs had a 120 millimetres (4.7 in) diameter and held up to 74 minutes of uncompressed stereo o digital audio or about 650 MiB of data. A variety of CD-based storage formats were developed: CD-ROM for general-purpose data storage, 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), Enhanced Music CD, and Super Audio CD (SACD) which may have a CD-DA layer.

Higher capacity DVDs followed on from CDs and are used for digital video storage.