Short for Application System/400
, a line of IBM minicomputers
introduced in 1988 (though today it isn't called minicomputer nor mainframe- it is now called an enterprise server]). AS400 machines has two variants: the white and the black box.
AS400 has proven itself to be one of the most reliable, efficient, fast and secure rig today even with its "jurassic" nature and programming style (commonly RPG and CL). As a matter of fact, many large companies today are still run by AS400 like 3M and other banking and telecommunication industries. Funny how a 15-year old system runs these companies.
Additional info: not all workstations accessing AS400 are dumb terminals
. Today, we have these AS400 emulators
running on windows platform (e.g. Rumba or better yet, the AS400 PC-based itself).