By this time, the release of the first microcomputer systems in 1975 had quickly led to the introduction of Altair BASIC, the first version of what would soon be known as Microsoft BASIC. MS BASIC was patterned on BASIC-PLUS, and thus ultimately the Fifth Edition, but lacked indenting, MAT, and other features. It also added the codice_96 and codice_97 functions, breaking the three-letter convention. As the number of microcomputers grew, and turned into the home computer market in the late 1970s, MS BASIC became the "de facto" standard.