The super audio CD:

When the compact disc, CD, was introduced by Philips of the Netherlands and Sony of Japan in the early 1980s, pulse-code modulation (in practical use), on which CD technology depends, was still young (introduced by the Japan Broadcasting Corporation, NHK, in 1967). In essence, the CD is the medium that introduced most people to digital audio reproduction. Since the introduction of the CD, various aspects of digital audio engineering have been enhanced considerably and have made possible the Super Audio Compact Disc.