Hypothetical HP 15CII or 34S


I was just browsing through Archive 14 when I saw a very interesting thread there for a "hypothetical HP 15CII". The picture by Chris Woodhouse is very promising. I thought I would suggest a similar idea but so as not to confuse it with Chris's idea I've renamed it the "hypothetical HP 34S". Here's a picture of what it might look like:

You might notice in the picture the following:

- The ENTER key has been brought back in the horizontal orientation, which in my opinion makes entry easier

- The keys are in color-coded groups to facilitate quick location of a desired group; white for the number keys, light grey for the stack manipulation keys, a darker grey for the programming keys, and olive green for the trigonometric keys

- The keys are of the beveled type used in the Woodstock and Spice series; this is so that there need be only one legend above the key, namely the gold legend, while the blue legend resides on the bevel; in my opinion this design should have been kept by HP because it leads to a less uncluttered keyboard appearance

- The case is of the Pioneer type, with rounded corners, which I find easier to hold than the square corners of the Voyager type

I'd appreciate hearing any comments on the design, and thanks to Chris Woodhouse for the original suggestion.



It would be nice to have friendly LEDs but to get any useful battery life I'd guess you would need those 4 'D' cells that you have listed in your subject heading.



Hi all,

I would actually start from the 42s rather than the 15c as a base... Valentin, if you read this don't kill me ok... :)) The 15C is a wonderful machine, but I think that the 42s was more than a worthy replacement to it: Yes, the 15C had some unique advantages (the size, weight an classy design, the matrix descriptors with names), but I would not trade them for the huge advantages of the 42s (unlimited labels to keep loads of programs, speed, alphanumeric displays of program steps and prompts, 41 compatibility). Granted, the 42s is a bit more bulkier and is not as classy as the 15C, but it can still fit in a shirt pocket and is still far less bulky than the newer 33s. I also liked the sobriety of the keyboard, and the menus which some find ennoying are very fast and clever to me... There is no way all functions of the 42s could fit on the keyboard !! I just did not like the 2-stroke alpha entry, which was not troublesome for variables thanks to the menus, but made the 42s unsuitable to keep long textes. The 41, in my view, had the right balance between accessibility and clutter, with one shift key but one alpha mode.
What about starting with the 42s, and making the following changes:
1/Use the horizontal classy shape of the 15C
2/Have a direct alpha entry like the 41
3/Import the two goods unique features of the 32sii/33s world: the fraction mode, which is very unique, and the equations with multivariable solver, very useful when equations are too complex for RPN. But add editing facilities like in the 17bii/19bii world... lack of edititing capabilities is very frustrating on the 32sii/33s...
4/Add a USB port to backup and import programs from/to PC.

This would be my dream calc...


100% agree!!

Just give the USB some kind of programmable I/O instructions, so if someone would like to design a controller, data logger, expansion box, etc., it could be done. And please also import time functions, alarms, etc. from the 41CX. Also add some units conversions.


I agree, except in one thing:

"...and the equations with multivariable solver, very useful when equations are too complex for RPN."

I like the RPN multivariable solver of the 42s. What are those "too complex equations"?

In fact I'm writing a RPN multivariable solver for HP-41C inspired on the HP-42S.



In fact I'm writing a RPN multivariable solver for HP-41C inspired on the HP-42S.

I would like to see that solver, Guillermo, although the "Karl's method" for the 15c works in the 41 too...



You can download it from
or directly from

I would like to know your (and others) comments.



Hi Guillermo,
Thanks a lot for your solver ! I will try it :)
What I actually mean with complex equations is that if you have an equation which is long and involve a lot of variables and terms, programming it with RPN is not easy. You need to store intermediate results in registers as the 4-level stack is not sufficient anymore, and you would be much better off entering it the natural way, like on BASIC computers, Casio FX-4000P/7000G, or algeabraic expression in the HP-48 world. In that sense, the 32SII/33S does a good job, even though you cannot edit the equations once entered...
Thanks and cheers,


Paradoxically, that is one great advantage of the 33s (probably the 32sii also, but I haven't checked): When you enter an equation as part of a program, when it is evaluated, the stack is not used, and the value of the equation is pushed onto the X register.

In this case, due to the limited stack (I prefer the unlimited version), sometimes = > enter (actually, it is nice to see them working together).


My personal contribution for a hypothetical HP-42SX (screenshot from "Emu42 for Pocket PC 2002" - emulator by Christoph Giesselink, KML by myself):

Best regards,

Erik Ehrling (Sweden)


Can we get this KML? It is awesome! I have the Windows version of the HP-42 emulator.

Good work!



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