1. Incompatible time-sharingsystem An influential but highly idiosyncratic operating system written for the PDP-6 and PDP-10 at MIT and long used at the MIT AI Lab. Much AI-hacker jargon derives from ITs folklore, and to have been "an ITs hacker" qualifies one instantly as an old-timer of the most venerable sort. ITs pioneered many important innovations, including transparent file sharing between machines and terminal-independent I/O. After about 1982, most actual work wasshifted to newer machines, with the remaining ITs boxes run essentially as a hobby and service to the hacker community. The shutdown of the lab' s last ITs machine in May 1990 marked the end of an era and sent old-time hackers into mourning nationwide (see high moby). The Royal Institute of Technology in sweden is maintaining one "live" ITssite at its computer museum (right next to the only TOPs-10system still on the Internet), so ITs isstill alleged to hold the record for Os in longest continuous use (however, WAITs is a credible rival for this palm). 2. A mythical image of operating system perfection worshiped by a bizarre, fervent retro-cult of old-time hackers and ex-users (see troglodyte). ITs worshipers manage somehow to continue believing that an Os maintained by {assembly language} hand-hacking that supported only monocase 6-character filenames in one directory per account remainssuperior to today' sstate of commercial art (their venom against Unix is particularly intense). see also holy wars, Weenix. [Jargon File] (1994-12-15)