PDP-10/its: Incompatible Timesharing System

I still have some muscle memory for TECO.

Those example programs... holy cow. After that, I don't know if I'll ever feel bad about my code being unreadable.

I wrote a couple of programs for ITS after it was resurrected.

Tetris: http://web.onetel.com/~hibou/ITSter.txt

Conway's Life: http://web.onetel.com/~hibou/life.txt

ITS page on Ward's Wiki: http://wiki.c2.com/?IncompatibleTimeSharingSystem

(Incidentally the correction to the wiki article in file names is wrong: file names were two words, each of six characters.)

Steven Levy's Hackers (http://www.stevenlevy.com/index.php/books/hackers) contains the history of its development. More information on ITS, and how to run it, can be found at http://its.victor.se/wiki/

And coolest of all, someone's got a PDP-10 running ITS on a FPGA: http://fpgaretrocomputing.org/pdp10x/

Around 1982, I had an account on MIT-MC, an ITS computer. I was not an MIT student -- rather, a curious teenage hacker from DC. I'd found a text file with 'interesting modem numbers,' and one of those was to a DoD TAC (basically, a dial-in). I recall the text file had a note saying how to connect (via NCP, not TCP/IP) to MIT-MC.

I connected, and remember playing around (as we did) at the login prompt. I probably tried to login as 'guest' or something, and the result was basically, 'There's no user by that name. Do you want an account?' Of course, I said yes -- and shortly received my own account.

Stallman may have been sponsoring logins for folks like myself; he definitely was a little later when I got an account on MIT-AI (or was it MIT-OZ?), which was by that point a TOPS-20 machine.

ITS was a very bizarre system, really with its own social culture. Even in 1982, it felt strangely archaic. The debugger-as-shell was definitely an interesting concept.

Once I accidentally deleted a file. I felt awful, and emailed one of the admins, assuming they'd kick me off. He was like, 'Ah, no worries. We'll just restore it from tape.'

Relating this back to the topic of OS history, it's interesting to note that PDP-11 was the original BSD UNIX platform, and that 2.11BSD for PDP-11 still receives occasional patches (the most recent one I can find is from March of last year).

And as a former "home" MicroPDP-11/83 owner, I can attest that it was indeed fun to put together and write code for.

With that said, while probably not what you have in mind when you speak of "single-board systems", the DEC Professional 3xx (325, 350, 380) is a desktop PC built around a single-board PDP-11 CPU. And most (all?) MicroPDP-11 systems are built around a Q-Bus CPU board, and, excluding bulky options like multi-port serial patch panels, open-reel tape drives, and large (around 150 lbs. and 6U for my 456MB RA81) hard drives, aren't much bigger than a modern full-tower or >1U rack server, though they require considerably more electrical power (generally not too much for a dedicated 120V 15-20A household circuit, however, unless kitted out with, e.g., more than one of the aforementioned RA81 disks).

Both are "single-board systems" in the sense that the CPU, and in some cases RAM, is contained on a single board, though you'll need one or more I/O boards to do anything useful with them. Which, depending on your idea of fun, you could, I suppose, build yourself — there was, after all, a time when PDP-11 CPUs weren't an unusual choice in larger embedded systems.