PDP-1 Lisp - manual page added - but looking for PDP-1 Lisp programs

[Oscar Vermeulen]

So I added a manual page for those who want to explore Lisp. Quite a historical piece of software, and as it turns out, usable as well.

Page link:

https://obsolescence.dev/pdp1-lisp-introduction.html

The page includes a .md training file to make Claude Code or ChatGPT a PDP-1 Lisp tutor (as I needed that, I must admit). Quite effective!

But the question is - I've gone through all the paper tape archives, but could not find any Lisp programs. Does anyone know where to find them? Always good to learn from other's code :-)

Kind regards,

Oscar.

[Bradford Miller]

Let me also add some other online references: http://www.softwarepreservation.net/projects/LISP/book/III_LispBook_Apr66.pdf

Lisp for the PDP-1 (source) https://simh.trailing-edge.com/kits/lispswre.zip (NB: this contains a RIM file)

Also note that the Lisp 1.5 manual is still in print! (I even have a copy, along with Allen’s book “Anatomy of Lisp” which came out in 75, but has a lot of implementation information relevant to the earlier versions (Allen was part of the team that created Stanford’s 1.6 version of lisp). There’s more info here, which also talks about the PDP-1 and historic paper tapes: 1.5 at Amazon: 

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[Oscar Vermeulen]

Brad,

On Sunday, September 21, 2025 at 4:27:02 AM UTC+2 bradford...@gmail.com wrote:

Let me also add some other online references:

Thank you! -- 

 

 http://www.softwarepreservation.net/projects/LISP/book/III_LispBook_Apr66.pdf

That is a great resource. In fact, that opens up the use of PDP-1 Lisp for real, not just as a dive into software archeology. An to my astonishment, I see Fischer Black is one of the authors - I did not realise that he was at BBN, involved with Lisp, before he became a famous economist... in my previous working life as an economist, his work pretty much was the foundation of all I did. How strange to encounter him then in this other world again!

 

Lisp for the PDP-1 (source) https://simh.trailing-edge.com/kits/lispswre.zip (NB: this contains a RIM file)

Yes, in fact that is the lisp tape we used - and the included macro cross-compiler  as well. I found two other versions of PDP-1 Lisp. They are more recent, but one requires the storage drum and the other is for the TS Executive (operating system) on (I think) MIT's strongly hacked PDP-1X machine. Certainly the drum version is on the to do list, but won't run at present.

along with Allen’s book “Anatomy of Lisp” which came out in 75

Huh! I found the link to the book here: https://dl.acm.org/doi/pdf/10.5555/542865. 

So it looks like Allen is the one who converted Lisp to the generic (non-MIT) PDP-1 and his version is the one we actually use? 1964 sounds right. I did wonder where the simh Lisp tape came from as it is not in any of the bitsavers directories.

Thank you! I started out thinking there was no more documentation on PDP-1 Lisp, but the first link is a complete introduction, course and more. Perfect.

I had not intended to truly delve into Lisp, but with that book at hand, I think I should... oh dear, another rabbit hole to jump in to :-) I'll update the web page with a link to these treasures.

Kind regards,

Oscar.

[Bradford Miller]

On Sep 21, 2025, at 6:07 AM, Oscar Vermeulen <vermeul...@gmail.com> wrote:

Thank you! I started out thinking there was no more documentation on PDP-1 Lisp, but the first link is a complete introduction, course and more. Perfect.

I had not intended to truly delve into Lisp, but with that book at hand, I think I should... oh dear, another rabbit hole to jump in to :-)

Well, rabbit hole of a lifetime for me. I still use Common Lisp (which has its roots in Maclisp) and to a much lesser extent Scheme to this day (I used an early version of the latter under ITS!). Thankfully we’ve solved most of the issues with lack of memory and somewhat clumsy function definitions in more modern dialects. Still, theory directly meets practice through Lisp if you’re into that sort of thing :-) (Referring to Alonzo Church’s Lambda Calculus).

For more modern treatments (won’t help you much with running Lisp on the PDP-1, but will help with understanding how to elegantly program in Lisp):

And for really advanced concepts (I’m still trying to wrap my head around some of these ideas):

There is of course a lot more advanced material available for later dialects, particularly common lisp (which doesn’t show up publicly until 1984 IIRC). 

A fun little project might be to write a Scheme interpreter for the PDP-1. It’s a rather small pedagogical Lisp (particularly the earliest “standard” definitions). If I think I can sneak a 1 into the house without SWMBO’s notice, I might do that myself :-)

Best wishes,

Brad

[John Kennedy]

I love Lisp and may have a problem collecting books about it 

[Flavio Villanustre]

John,

From the books on your bookshelves, Land of Lisp is a good smooth easy introduction, if others want to see what Lisp is about in a practical way. The little lisper, on the other hand, is in its own realm. Quite enjoyable, but a brain twister.

And on the complete opposite end of the spectrum, On Lisp, from Paul Graham, takes you to the deep end of macros, where Lisp programs code themselves (or, as they say, in Soviet Russia, Lisp programs you :) ).

Great book collection you have, John 

Flavio Villanustre

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[John Stout]

I just can't get LISP to run from these instructions Oscar.

I set EXTEND switch up, set the lisp.rim tape, and press READ IN (the tape reads in)

I put 7750 in the TW switches, press CONTINUE

I put 400 in the TW switches, press CONTINUE

I set SENSE SWITCH 5 up and ADDRESS to 4, press CONTINUE

 I can type into the terminal window but typing NIL<space> doesn't do anything. I've tried with START/CONTINUE but again nothing seems to work.

Running test.sh convinces me that all the switches are working.

I've tried with both the supplied lisp.rim and that in the archive (Lisp for the PDP-1 (source) https://simh.trailing-edge.com/kits/lispswre.zip (NB: this contains a RIM file)) but no joy.

I think all the other software seems to work fine (I spent an interesting hour or so playing Spacewar with my 10-year old grandson yesterday; despite being an iPad/Super Mario on the Switch child, he loved Spacewar (and consistently beat me), and just loved being able to do a gravitational slighshot around the start!): I've assembled and run the circle demonstration for MACRO, experimented with Minskytron, Pong and Munching Sqiuares, but LISP doesn't want to play.

Do you have any obvious things I can try? The sound isn't working properly but I'm assuming that's unlikely to be relevant, and proably a soldering issue.

John

[John Stout]

Personally I don't see the problem! I think I've 14 or 15 of those, plus Structure and Interpretation of Computer Programs (which I can't see).

I still haven't really got to grips with Let Over Lambda but I keep on trying!

John