Best of Show: PDP-7 and PDP-11/40 emulation | Hacker News Reader

Best of Show: PDP-7 and PDP-11/40 emulation

ioccc.org

157 pointswscott27 comments

Here is the C program: https://www.ioccc.org/2018/mills/prog.c It is a PDP-7 emulator that can boot the most ancient known snapshot of Unix. This is running Unix from 1969 where the compiler is 'bc' (no 'cc' yet) then, he wrote a PDP-11 emulator in PDP-7 assembly and uses the PDP-7 to emulate a PDP-11 to boot BSD 2.9.

For context, this is from The International Obfuscated C Code Contest https://www.ioccc.org/

Also, the 26th IOCCC has now started, if you are inspired!

[ Submitted as news: https://news.ycombinator.com/item?id=18764925 ]

Hmm, seems neither current gcc nor clang can compile this even with -ansi or -std=c89

The submission has a Makefile that works fine for me. It needs several things defined by -D for configuration options for the emulator.

https://www.ioccc.org/2018/mills/

Ahh thanks!

In my case it exits the shell upon loading ./v6. I compiled it with gcc 4.2 under OpenBSD 6.4. In happens the same with clang6.

IOCCC Judge here:

If you are using an xterm, you might try using "xterm -hold".

It seems that the termios structure is getting (re)set with some invalid values and some systems (one report from NetBSD) cause the terminal / shell to abort. We are figuring out how to do an update to fix this issue.

I laughed out loud when I got to the part about the PDP-11 emulation being written to run on the emulated PDP-7. That cranks up the hack value to 11.

The Turducken of software.

It's not a true turducken until someone takes the author up on their suggestion to in turn emulate a VAX 780 on top the PDP-11/40 here.

Turduckens+ all the way down...

+A recursively structured arrangement of Turing Machines.

We are in the strange situation with these emulators that all code ever written can be executed today, no problem. Have some Fortran-II code for the IBM 1401? No problem. Want to run some Analytical Engine code (a machine that couldn't even be constructed)? No problem:

https://www.fourmilab.ch/babbage/emulator.html

Can you really say that this early code is obsolete? I think not, it's just different.

That Turing guy was on to something..

Dolphin runs Wii. Code, Xenia does XBox360 - but the future for XBoxOne emulation looks bleak.

This is amazing.

Make sure to view it on a sufficiently wide browser to see the ASCII art of a torn piece of punched paper tape.

The program would be impressive if it was clearly written and commented.

The contest is about obfuscated C. Clearly written or not, I'm impressed.

The binary on the paper tape seems to be ascii (with a parity bit) reading "pdp-7emu.s".

If anyone wants to mess around with a PDP-11 simulator, you can get it up and running with Docker in 1 command.

Details are at: https://nickjanetakis.com/blog/run-the-first-edition-of-unix...

Way back in the early 80's when I was in high school I had an off campus class where I took a course on PDP-11 assembly language. Sadly we had to run our code in a PDP-11 emulator on a DEC System 10 and it was incredibly slow but I do remember how much I liked the PDP-11 instruction set. I wish I had kept the book from the class.

All the old DEC manuals are online. For example, the PDP-11/40 system manual:

http://bitsavers.informatik.uni-stuttgart.de/pdf/dec/pdp11/1...

Can anyone explain the background of this for a youngin like me whose first computer was Windows XP?

The short version is we have gone so far back in the history of UNIX that we don’t have filesystem paths yet.

Incidentally, the same was true of MS-DOS: no paths in version 1, only drive letters; directories and paths were introduced in version 2. However, early UNIX doesn't seem to have drive letters...

Where do people like this exist and how can I hire them? Really...

typo: "Thompson re-wrote a filesystem emulation he had been experementing with" should be experimenting

This is the best thing I have read this year. I expect I will still be able to say that next month.

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