Fun with Emulation #3 - Running a PDP-11/34 with RSTS/E under Ubuntu Linux

The first "real" computer system upon which I ever laid my hot little hands was a PDP-11/34 at Western Kentucky University.  I was attending WKU during the summer between my 11th and 12th-grade years of high school, and one of my typical "go see what's out there" walkabouts led me to the "computer center."  Now, there were several signs posted which suggested that ONLY those students taking SPECIFIC Computer Science classes could gain access to "the PDP", but I explored the terminal room anyway.  One of the admins came out and started throwing a tantrum about the mess left by all the students.  Inspiration hit - I quickly offered to stop by every afternoon and clean up the terminal room, if I could only get access to the PDP...and the deal was done.  I had no idea that TI Silent 700 terminals generated SO much waste paper.

Nonetheless, I was in.  I started playing around with RSTS/E, which was one of DEC's major operating systems in the educational arena, and BASIC-PLUS-2 was THE language of choice.  (Hey, this was 1980.)  One fine day, I was browsing the system tables and noted that there seemed to be 32 terminals connected to the system, although I counted only 24 in the computing center; when I asked, the admins just said, "Well, he gets a key to the closets."  As it turned out, these guys had commandeered closets (scattered throughout the science complex) and wired in either Silent 700 or--*GASP*--LA-36 DECWriter hardcopy terminals.  SCORE!  Printouts on which you could actually TAKE NOTES!  I spent a great deal of time in those closets, and I found that, yes, one COULD write device drivers in BASIC, given enough system calls.  One could also wreak havoc upon peripherals with PIP if you didn't know what you were doing.  I did both.

Bringing back RSTS/E turned out to be the easiest of my emulation projects to date.  After compiling the pdp11 simluator from the SIMH package (linked below), I found the RSTS V9 Archive, which provides a prebuilt, full image of RSTS/E V9.6 on an RP04 disk image; the latter site even provides configuration files for SIMH.  This was literally a ten-minute project, and I had RSTS/E up and running under Ubuntu Linux.  (RSTS/E is text-based only, so I won't bore you with a screenshot.)  If you're longing to write code like:

100 OPEN User_keyboard$ AS FILE #1

Tmp$ = SYS(CHR$(118)+CHR$(18))

LINPUT 'Enter the first line of text';User_input$

...then hie thee to the links below.

The Computer History Simulation Project

RSTS/E V9 Archive

 

Beer CAN Aid Your Memory!

As I've been playing with emulators, my knowledge of programming languages has been put to the test.  Sure, many of us can say that we've written code in dozens of languages, but how many of them can we REALLY remember today?  I'll be the first to admit that my recollection of many languages is somewhat fragmented and/or jumbled.

I was looking around for some ALGOL code when I happened across this wonderful resource.  Put simply, it celebrates the "99 bottles of beer" song from our childhood by providing code examples (in 1400+ programming languages!) that print the song in its entirety.  If one stops to think about it, such code must use simple computation, looping/test constructs, and text manipulation; I find reviews of this source code to be a WONDERFUL memory-jogging tool.  For instance, here's the MACRO-10 version I used to test my PDP-10 emulator. Enjoy!

99 Bottles of Beer

Fun with Emulation #2 - Running a DECSystem-10 on Ubuntu Linux

Fun with Emulation #2 - Running a DECSystem-10 on Ubuntu Linux

I can honestly say that the 36-bit DEC-10 was the machine that took me from "gee whiz, this is keen!" to actual coding/hacking. If one could schmooze a faculty member into signing the authorization form, students could get access to the DECSystem-10 (#1059) at the University of Louisville at a screaming 1200 baud.  I fell in with a group of similarly minded folks who were happy to share their knowledge, and that was that.  Within a week or so, I was writing my first assembler code; to this day, the early PDP instruction set is THE most intuitive, mnenomic assembler I've ever used.  I wrote my own (condensed) version of SYSTAT, played ADVENT (considered the first text-based adventure game, inspiration for PC Zork) and DECWAR (one of the greatest of the early computer games), and dove deep into machine internals for the first time.  I still remember the night we hacked the controller on one of the university's high-capacity copiers with a paperclip (this was 1981, remember) and spent 4 hours pirating the DEC-10 Monitor Calls Manual and Hardware Reference Manual.

In my current exploration of the emulation universe, I ran across SIMH, which emulates dozens of old minicomputer and mainframe systems.  I was delighted to learn that the PDP-10 is among them, and that ready-to-run images of TOPS-10 7.03 exist.  The build under Ubuntu Linux was near-trivial, and bringing TOPS-10 up went smoothly as well.  The result?

It may not be as visually impressive as are some emulators (notably Hercules Studio, about which I've already written), but it was incredibly satisfying to be working with MACRO-10 once more.  The TOPS-10 image I loaded supports COBOL, FORTRAN, BLISS-36, ALGOL and (of course) assembler, so my next project will be building DECWAR 1.2 from source.  In these days of IDEs, visual editors and code management systems of all types, there's something...GOOD about plain old text-mode coding.

If you want to join in my wave of digital nostalgia, you can find emulators and TOPS-10 images at the links below.

Next up: RSTS/E, or "Writing printer drivers in BASIC?!"

DEC PDP-10 Emulation
TOPS-10 pre-built image