HP 75 Assembly Language


Does anyone know about an assembler for the HP 75, running on the machine itself, and about documentation of the internal structure of the calculator?

A book exists named "HP-75 Assembler Handbuch" (German language).
It is mentioned in a catalogue of W&W Software Products (German company) in the year 1986. The description says that the book was written by Michael Hartmann, specialized in the HP 75, that the book contains detailed information about the internal structure, and that it comes with a cassette or disc containing several lex-files for an easy start into HP-75 assembly language programming.
Anyone reading here who has got that book and lex files?
Or is there a similar introduction to HP-75 assembly language in English?


Did you try Series80.org ?




To my understanding the HP-75C/D CPU was the CMOS version of the CPU used in the HP-80's series.

So, the documents for the 80's should be a good source of informations for the 75.

A lots of informations are available in the NOMAS volumes, the PPC Computer Journal and to a lesser degree in PPC-CA, CHHU, DATAFILE journals.

Also, a lot of interesting sites can be found if you search for "1980s Vintage Computers" or "HP_Series-80".

If you want to program in assembly language ...

There are several free assembler/deassembler available for the 80's that could be the base for a new one for the HP-75.

Of course it would need to be modified to generate the valid file format and use the appropriate entry point table.

Another way is to load the HP-75 Forth language with the assembler/deassembler extension from Forth Age.


Edited: 30 Sept 2012, 10:40 a.m.


Thank you for your hints, Sylvain.

I found the forth.org page and the forth assembler/disassembler for the HP 75c, but I am not sure whether that package contains the mentioned machine code assembler / disassembler extensions (like the forth/assembler module for the HP 71 does); probably it doesn't. Any idea where I could find such extensions, preferably documented?

Theoretically, in order to create HP-75 mcode routines, it's possible to study the NOMAS listings, use a 80 series development platform and adjust the output files, but that certainly is the very hard way. That's why I am still looking for a more convenient solution, like the mentioned German book which seems to be kind of tutorial for HP-75 mcode programming - including a disc providing mcode assembler and disassembler.


I have the “Assembler-Handbuch für den HP-75” from W&W - app. 170 pages - and a cassette with the files. The assembler is a HP-75 BASIC program that reads a text-file and converts it to a LEX-file.

W&W still exists and owns the copyrights to the manual and software. Without their permission I cannot copy the material.

On the SWAP disks (SWAP09 and others) you can find another HP-75 assembler in BASIC called ASM. It is based on the HP-75 assembler described i PPC Journal V12N5 p30.


Hello Jakob,
I am very interested in your book and software and will try to get a permission by W&W. But I'm not sure whether I will receive an answer from them at all. I already wrote an email to W&W and asked about the assembler book, but they didn't answer. Generally today's successors of the companies that produced HP calculator accessories aren't interested at all in that vintage stuff. On the other hand, when they gave up commercial interest, they shouldn't have anything against copying of those ancient books and software then.
In case I get no answer from them: Would you sell me book and software? I offer you $ 150,-


First download the zip and the manuals from the forth.org site.

The zip file contains the various forth images and the individual forth file blocks.

Open up the manual, go to page 3 and you will see the description of all the files.

The manual also shortly describe the CPU and how to use the forth package.

The HP-75C & IO-ROM NOMAS (3 PDF) are available from this site.

I am not aware of any user friendly toolchain ever available for the 75.

In PPC-COJ V2N3 May 1983 the Dave Conklin letter list the dev tools available for the 75.

Also, in PPC-COJ V3N3 May 1984 P.23 Pete Verenkoff talk about it's 75 self hosted lex file assembler.



Thank you, Sylvain!
I will read through the denoted sources.

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