Compact disc

The compact disc (CD) is a digital optical disc data storage format co-developed by Philips and Sony to store and play digital audio recordings. It employs the Compact Disc Digital Audio (CD-DA) standard and is capable of holding uncompressed stereo audio. First released in Japan in October 1982, the CD was the second optical disc format to reach the market, following the larger LaserDisc (LD). In later years, the technology was adapted for computer data storage as CD-ROM and subsequently expanded into various writable and multimedia formats. By 2007, over 200 billion CDs (including audio CDs, CD-ROMs, and CD-Rs) had been sold worldwide.

Standard CDs have a diameter of 120 mm (4.7 in) and typically hold up to 74 minutes of audio or approximately 650 MiB (681,574,400 bytes) of data. This was later regularly extended to 80 minutes or 700 MiB (734,003,200 bytes) by reducing the spacing between data tracks, with some discs unofficially reaching up to 99 minutes or 870 MiB (912,261,120 bytes) which falls outside established specifications. Smaller variants, such as the Mini CD, range from 60 to 80 mm (2.4 to 3.1 in) in diameter and have been used for CD singles or distributing device drivers and software.