The Atari ST was a home computer released by Atari in June of 1985. The letter "S" and "T" were short for "Sixteen/Thirty-Two", a reference to it's 16-bit bus and 32-bit CPU; the Motorola 68000. It was designed to compete with the Macintosh and Commodore Amiga computers. The ST ran a version of the CP/M operating system and had 512 kB of random access memory, expandable to 4 MB. It is notable for being the first home computer to feature built-in support for MIDI audio.