Can anyone comment on the Lygea HP15C emulator?


Being quite amazed at the typical eBay prices for HP15C (typically $300+ for scratched/incomplete ones), I was looking for some good Windows-based emulation.

I have found a Windows CE / pocket PC emulator done by Lygea (see

Do any of you use this? Thanks for your opinion.


As far as I can see, you can download and try it for 14 days for free.

You could do that and then post your experiences here ;-)



Here's some enthusiastic opinion (and endorsement), if a bit brief:

HP-15C emulator

Anyway, this product is not an "emulator" at all, but a simulator. A real emulator runs a bit-perfect copy of the original ROMs in an emulated original CPU. This exactly mimics the full behaviour of the machine being emulated, bugs and all, limitations and all.

On the other hand, this HP15C simulator just tries to imitate more or less what the original 15C did, but it goes on changing things (more items in the display, more program steps, more memory) and you can be sure that many original 15C programs won't run on it as they would run on a real or emulated HP-15C.
I can certainly write a number of perfectly legal HP-15C programs that won't run as intended on it, if at all. And for nearly all HP-15C programs doing some kind of extensive calculations, you can bet that your simulated results won't match the real ones.

Mr. Kahan and the rest of people involved in the design of the HP-15C algorithms took really extreme efforts to guarantee accuracy, stability, convergence, and such, to an extent never before seen (and probably after, as well) on a handheld calculator. I very much doubt that this simulator does include such ultra-finely tuned algorithms, and most probably relies blindly on greater native precision (typically 16 digits) to cater for any lack of refinement.

In a worst-case scenario, you could find yourself with the simulated Solve failing to converge to the correct solution (a la HP12C Platinum), failing to find an existing solution, or finding a solution that isn't, you just have a look at the HP-15C Owner's Handbook and HP-15C Advanced Functions to see the many pitfalls awaiting for non-optimized algorithms to fall into. I guess the people who wrote the routines for the 12C Platinum did just that, blindly relying on greater native accuracy and faster CPU, and we all have seen the results: non-convergence, lack of reliability, and utter inefficiency.

In a nutshell, I think that calling this product an "emulator" is a gross misrepresentation, and I wouldn't trust its answers, specially when using the advanced functions: matrices, complex, solve, integrate. I trust my HP-15C, because I know the who's and the what's behind it.
Just read this unbelievably good article by Mr. Kahan, who's one of the fathers of the real HP-15C, and once you've read it, see if you would trust an HP-15C simulator to deliver the goods:

Mathematics written in sand (105 Kb PDF document)

If you really need an RPN emulator for your PC, you could do much worse than to get one of the freely available 41C emulators. One of the very best does perfectly emulate an HP-41CX, synthetics and all, complete with Advantage ROM and other modules also perfectly emulated. Actually, it's pretty indistinguishable from having a real, loaded HP-41CX inserted on your very screen, photorealistic cosmetics included.
There's almost nothing you could do with a real or emulated (not simulated) HP-15C that you won't be able to do with this emulated 41C. I use it to write all my 41C programs and articles, for instance. And it's free. I don't know if some version is available for PocketPC or other PDA devices, but certainly a real emulator is the way to go.

Best regards from V.

Edited: 21 July 2003, 8:35 a.m.


I know that emulators are available for some Classic models (35, 45, 55) the 41 and various Saturn machines.

But does there exist a real honest-to-God emulator for any of the Woodstocks, Spices, or Voyagers?

I haven't looked at everything that's been published out there, but all I've seen are simulations, which are OK, but not the Real Deal.

I'd like to do an emulator but don't have enough info yet.


- Michael


There is an excellent HP25 simulator here at the MoHPC (Simulators page), as the source code is available, you can adapt it to run off-line...


I do like this simulator. The only problem I have with it is that it is very slow to respond to button presses. Sometimes it takes a couple of seconds for the display to update. It's very disconcerting.

Would running it off-line make it any faster?

(I use the HP-45 emulator a lot. It has a less-polished user interface but at least it responds instantly.)

- Michael


Posted by Valentin Albillo:
"(...)Best regards from V."

Whoops, V is already taken lol, gonna have to change it. I guess ill stick to X-V or something like that.


"|V2|" (not definitive) AKA "\V/"


I gave it a try on my Toshiba PDA and I was favourably impressed. I didn't try it for longer than the 15 day trial period however.


I have used it in trial mode for a while and it is excellent! You have to get used to the sideways screen but that suits the calc well.

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