CD
CD (English: Compact Disc), is an optical disk used to store digital data, was originally developed for storage of digital music. CD was released in 1982 and is still the standard storage media for commercial recordings. Before the CD has not yet been invented, the sound system is an analog signal, the source of music is mostly 30 cm diameter of the dense discs, radio and tape recorders, CD inventions before there is no digital sound, so CD can be said to be since the transistor The greatest invention. ...