The MiniDisc (MD) is a magneto-optical disc-based data storage device initially intended for storage of up to 74 minutes and, later, 80 minutes, of digitized audio. In the form of Hi-MD, it has also developed into a general-purpose storage medium.
MiniDisc was announced by Sony in September 1992 and released that November for sale in Japan and in December for the USA and Europe. The music format was originally based exclusively on ATRAC audio data compression, but the option of linear PCM digital recording was later introduced to attain audio quality comparable to that of a compact disc. MiniDiscs were very popular in Japan but made a limited impact elsewhere. The MiniDisc system can now be considered obsolete as the last MiniDisc recorder/player was finally discontinued in 2011. The discs themselves are still available (as of Sept 2012).
Read more about MiniDisc: Market History, MD Data, Recording Modes