This OS was implemented on DG minis in about 1970 by Educational Data Systems.

Dan Paymar, one of the EDS cofounders, hired me to help him complete a one-user diskless Basic Interpreter in Summer 1969. I remember debugging the MAT INV operation by listening to the funny patterns of noises the FM radio made as MAT INV ran; you could hear it processing matrix rows. We did this on Data General Nova serial #3, using a truly awful teletype-based text editor and assembler that read and wrote paper tapes. We produced mountains of "chad" from paper tape holes, ugh. And you haven't lived until you've made a 1000' paper tape and the 3 year old kid belonging to your boss tears it in half.

EDS wanted to sell "educational" computers to schools but one terminal wouldn't serve multiple students so we built a 4 user memory-only standalone Basic interpreter with bad but workable timeslicing in 16Kb core memory. Hardware multiplexors for multiple bit-serial devices (in our case, Teletypes) barely existed and were really expensive, so we built a dirt-cheap 16 bit parallel output register with one bit per terminal, and I built a device driver using the 1000hz built-in interrupt to serialize the ASCII bits being sent to the output ports. This continuously burned about 35% of the CPU even when nothing was being transmitted, but still left plenty of CPU for the timesharing Basic. We could drive 16 Teletypes full blast (110 baud) at the same time, making one hell of a racket.

In Summer 70, the company got a head-per-track disk drive, and (zounds!) 32kb of core memory, and Paymar asked me to write a version of the BASIC that stored program files on the disk. I was a bit contrarian and being left unsupervised :-} I inverted the problem to produce a multi-user disk operating system that would would run a BASIC interpreter as one of many applications, initially called Alice. The head per track drive meant Alice could swap users remarkably fast and the resulting response times to the teletypes was still quite good. The disk also gave us space to build a respectable file system where files actually had built-in record description metadata. Alice could also run a text editor and an on-line assembler using disk files so we could finally avoid using the paper tape reader and high speed punch! All of this is done in hard core DG assembly language. My college buddies Steve Sternitzke and James Neighbors were a major part of this exercise.

This was frankly pretty impressive: a real timesharing system on a minicomputer. Yep, earlier than Unix. I've been stunned for my entire career that I got do to this when nobody was looking.

Six months later, EDS ran into a financial troubles and I went on to do other things (eventually building an incremental BASIC compiler for Keronix DG clone computers and other operating systems https://retrocomputing.stackexchange.com/a/4541/6744). EDS renamed the OS to IRIS and started to sell it as a Business Basic system. Apparently it was pretty successful in that market. I came back as consultant a number of times, the last time sometime in the early 80s to help them figure out how to get 64 users running on that a DG clone called "point 4" (after the .4 ns cycle time) now made by EDS renamed to "point 4 corp". It was rather stupid to name the company after the cycle time of a product... sure enough, it got faster but the company name was stuck. Marketing people... sheesh.

I don't have a good timeline of what happened after I left. Any more stories of how it evolved would be interesting.

  • @paxdiablo: Great find! I can feel the rust scales falling off really old brain cells. Ah, coding in the 1970s....
    – Ira Baxter
    Commented Nov 14, 2018 at 2:20
  • 3
    Ira, weirdly enough, I've only just finished re-reading "The soul of a new machine" about the machines that immediately followed Nova. I wasn't cutting code in '69, I was only 4yo at that point, but I still like reading about the history.
    – user6464
    Commented Nov 14, 2018 at 2:35
  • 1
    @paxdiablo: Data General was a damn funny place. It spun out of DEC, the Nova being a DEC-internal competing design for their planned 16 bit computer product, for which the PDP-11 design won. The Nova was spectacularly successful because it was cheap, cheap because it was incredibly simple internally. Because of this it was easy to copy so was cloned several times, including by EDS itself. One of the clone makers, Keronix (I helped them design a clone!), had a plant burn down, and fingers were pointed at DG's president DiCastro but nothing was ever proven.
    – Ira Baxter
    Commented Nov 14, 2018 at 8:48
  • 1
    I went to High School in the mid 70's. They managed to upgrade to an Alpha Interactive Computing Environment (ALICE) system for the students while the administration went on about business using Unit Record Equipment. (It's hard to calculate payroll when your plugboard can't handle multiplication.) A favorite feature was that even with the console locked you could set the switches to 136310 octal (IIRC) and the O/S would halt the machine shortly thereafter. That effectively unlocked the console and you could "correct" your privileges before hitting Continue. BZUP anyone?
    – HABO
    Commented May 12, 2022 at 3:23
  • @HABO: Block Zero Utility Program BZUP ... yeah, we did what we had to do to make managing a finicky small computer possible. Not pretty, just possible :-}
    – Ira Baxter
    Commented May 12, 2022 at 14:13

2 Answers 2


You could start with the Understanding IRIS section of the Microtech blog.

There's quite a few articles on there about this OS, including a 2016 interview with one of the original designers, Dan Paymar. He may well still be contactable.

In fact he even mentions the guy who worked with him on the BASIC interpreter, a name that sounds like Bira Waxter, Zira Faxter, or something like that :-)


IRIS is now running on the simulator that was developed by trailing-edge.com. See www.nova-iris.net for extensive documentation on IRIS and a working IRIS OS for the simH simulator.

  • 2
    While this may be interesting, it doesn't address the timeline of the OS - except for the present time.
    – Chenmunka
    Commented May 21, 2019 at 17:21
  • @Chenmunka: Interesting enough, now we've established where it has ended up :-} All we have to do is fill in the points in between.
    – Ira Baxter
    Commented May 21, 2019 at 18:14
  • This does not provide an answer to the question. Once you have sufficient reputation you will be able to comment on any post; instead, provide answers that don't require clarification from the asker. - From Review
    – Raffzahn
    Commented May 21, 2019 at 21:04
  • @wizzwizz4 Sorry, but it's not an answer at all. Mentioning that an OS is as well running on some emulator doesn't add any information about the OS or it's timeline. If at all, it's a statement about the qualities of the emulator used - most definetly not anything that was asked about.
    – Raffzahn
    Commented May 21, 2019 at 21:10
  • @Raffzahn Looking into it further, yes, this does just seem to be a bog-standard hardware emulator. I was mistaken.
    – wizzwizz4
    Commented May 21, 2019 at 21:35

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