Incompatible Timesharing System

ITS, the Incompatible Timesharing System (named in comparison with the Compatible Time-Sharing System also in use at MIT), was an early, revolutionary, and influential time-sharing operating system from MIT; it was developed principally by the Artificial Intelligence Laboratory at MIT, with some help from Project MAC. In addition to being technically influential (both in the operating system itself, as well as applications developed on it), it was one of the projects most important in the original development of the hacker culture (as documented in Steven Levy's book Hackers).