The 520ST is the first personal computer to come with a bitmapped color GUI, using a version of Digital Research's GEM released in February 1985. 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 US$1.

The Atari ST is part of a mid-1980s generation of home computers with 16 or 32-bit processors, 256 KB or more of RAM, and mouse-controlled graphical user interfaces. This generation includes the Macintosh, Amiga, Apple IIGS, and Acorn Archimedes. "ST" officially stands for "Sixteen/Thirty-two", which refers to the Motorola 68000's 16-bit external bus and 32-bit internals.

The ST was sold with either Atari's color monitor or less expensive monochrome monitor. The system's color graphics modes are only available on the former, while the highest-resolution mode needs the monochrome monitor. Some later models could display the color modes on a TV.