What is Mini Disc (MD)?
MiniDiscs were announced in 1991 by Sony as a disc based digital medium for recording and distributing consumer audio that is "near CD" in quality. In 1993 Sony announced MD Data, a version of the MiniDisc for storing computer data.
There are two physically distinct types of discs: Premastered MDs, similar to CDs in operation and manufacture, and Recordable MDs, which can be recorded on repeatedly and employ magneto-optical technology. The disc itself is enclosed in a small (7cm x 7cm), convenient, cartridge.
Nearly 160MB for 74 min. in audio mode [140MB in Data Mode]