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ITS

ITS (Incompatible Timesharing System) was a famous OS developed by hackers at MIT's AI lab from 1967 to the early 1980's for the DEC PDP-6 and PDP-10 family. It was famous for being the antithesis of MIT's security-obsessed CTSS (Compatible Time-Sharing System), by being very hackable and so user rights were a matter of social respect and ethics alone, rather than the dictates of the system, which often limited performance and capacity of the system. ITS was driven by the hacker ethic. Richard Stallman, founder of the GNU project, got the idea of free software from his work with ITS.

• See Also A Brief History of Hackerdom - 3. The Early Hackers by Eric S. Raymond, and
• Open Sources Voices from the Open Source Revolution - The GNU Operating System and the Free Software Movement - The First Software-Sharing Community by Richard Stallman.
• or get some detailed information and a login to a running ITS system (is it emulated? Who cares, it runs the web server!) here.

• FOLDOC on ITS

• Richard Stallman discussed some ITS features in this lecture. See also this interview.

• Report on ITS's PCLSRing technique, by Alan Bawden:
  • Text version
  • HTML version by Joe Marshall
  • A mirror

• Newer paper about something like PCLSRing

• Steven Levy's 1984 book "Hackers: Heroes of the Computer Revolution" has a section on the ITS hackers. (The appendix contains the epilogue, but isn't online.)

• ITS 1.5 Reference Manual (1969) MIT AI Memo 161A (8.4Mb scanned postscript)

• ITS & PDP-10 terminology/folklore

• PDP-10 software, papers, etc.
• Vintage Computer Festival
• Joe Smith's PDP-10 page
• www.36bit.org
• PDP-10 emulators, including sources for ITS.