AIX is the brand name of IBM's proprietary UNIX operating system. Several different vesions of AIX have existed over time, some being eventually eliminated. The first of AIX was released in late 1989.
AIX had a reputation among its users for its maddening inconsistencies with other UNIX systems. A common joke about AIX is that it is an acronym standing for "Ain't unIX". (Compare GNU.) Another is "AIX and pains".
AIX is likely to be superseded in the long term by IBM's support for Linux.
Clever ideas in AIX include commands like chuser, mkuser, rmuser and similar things which allows for user administration much the way you administrate files.
wikipedia.org dumped 2003-03-17 with terodump