The ST was primarily a competitor to the Macintosh, Amiga, and, in certain markets, the Acorn Archimedes. The Atari ST is part of the 16/32 bit generation of home computers, based on the Motorola 68000 CPU, typically with 512 KB or more of RAM, a graphical user interface, and 3½'floppy disks as storage. The 1040ST, released in 1986, is the first personal computer to ship with a megabyte of RAM in the base configuration and also the first with a cost-per-kilobyte of less than USD$1.
The Atari ST is the first personal computer to come with a bit-mapped color GUI, using a version of Digital Research's GEM released in February 1985. 'ST' officially stands for 'Sixteen/Thirty-two', which referred to the Motorola 68000's 16-bit external bus and 32-bit internals. The first ST model, the 520ST, was released in June 1985.
The Atari ST is a line of home computers from Atari Corporation and the successor to the Atari 8-bit family.