Chess on HP41C


I found a post (ref 46884) in Google where a question was asked about a full chess version written for HP41. This post seems to have been deleted meanwhile. So, for the person who wanted to know something about this: here I am!



Hello!!! It's great to hear from you! You've probably forgotten but I bought your wonderful program back in the 80's. It was an impressive feat, one that I've been always in admiration of, regardless of the possible shortcomings that could be found.

The subject of Chess on the 41 came up recently, as I mentioned your program to Valentin Albillo, who didn't reply but Jim did, interested in getting a copy.

I offered so, but now that you're here, I would like to get your agreement, as I still consider you the "legitimate owner of the program" - author's rights, if you know what I mean.

Have you kept up with the 41 world? I remember I proposed to you a "CHESS ROM" , which undoubtedly would have had to be in MCODE to have the speed under control! Oh, those days were great, weren't they?

Again, great to see you're still around.

All the best from the Black Forest.
Angel Martin


Hi Angel, hi Claude,

am I right that you are talkin of that nice chess program on many private mag cards, which I also bought for about 50 DM back in the eighties ?

If yes, then Angel, please remmeber that it was a synthetic program with precompiled jumps, which filled the whole calc memory.

However, if Claude could supply the algos & listings, a conversion to ML could be possible.

BTW: the version of the program I have allows the big lady to jump over the knights at the opening, regardless of the skill level;-)




There is also a description of a CHESSROM 1 in PRISMA 3/85..... Someone knows anything about this?




Yes, this is the program (CH136 if memory serves), and yes, it had pre-compiled GTO's to eliminate the "superfluous" LBL lines and use up all the calculator memory (and to increase speed). I thought it was an incredible achievement, and I still maintain so.

Many moons ago I "decyphered" the program and reworked the listing, including the LBL lines and decompiling other niceties that Claude had built in as well. It runs like a champ on my HEPAX memory, including the 80+ data registers values required for the game.

A conversion to MCODE would be pretty close to the proverbial insurmountable task, but at least some piece movements could be written in ML to accelerate the general speed, while maintaining the main program in FOCAL.

At least this is my impression, could be wrong of course.



Hi Angel,
Thanks for your post. What is HEPAX memory? Sorry, I am out of HP world since long.


Hi Claude,

Would you consider to put it to the public domain (on this site for instance), so people like me who didn't have had the opportunity to see it yet, could test it?
Especially I would try it on my Emu41 emulator ...




That's it! The speed problem solved!

Now that we have Claude's permission, I'll send you a unprivated copy if you can post it on your site :-)



What is the URL of this webpage?
Can you inform me by e-mail ( when it is done?



Dear All,
Thanks a lot for your answers: it feels great to hear that you liked my program. When I distributed it some 20 years ago, I didn't get a lot of replies (neither good nor bad), even though I sold it about 200 times (if I remember well). Interesting to hear that the queen can jump in an illegal way; I didn't know that. The only error I know was that when there is only one playable move left and if it is by the horse, it wouldn't find it. I have never released this bug fix.
It recalls my student time and it was definetely exciting to start working with computers in those days. Today I am still with computers, but only do programming at home for fun (try: http:\\ Otherwise it is more management work that I do.
I am delighted about the idea to open the program to public domain as I haven't sold any single copy in the last 15 years...
The only thing: I don't have a working HP41 anymore. So feel free to publish it in any way you like, please make sure that it always makes reference to its author. If needed, I might be able to find a version of non-private cards, but I would have to search some time at home.


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