HP-34C Emulator


Last year I got an emulator for the HP-34C for iPhone and overall I love it. The solve, integrate, gamma and other functions all work flawlessly.

The one problem I find is that if I have more than 2 labels the app gets confused. The original HP-34C is supposed to have 12 addressable labels: 0-9 and A & B. If I write a program with only two labels it usually functions correctly. However if I add more labels, the GTO and GSB functions cannot locate them. Sometimes the app just freezes and other times a GTO will just land in the middle of a subroutine. I've talked with the developer about this and he's very nice, and explained that he used microcode dumped from the physical machine, but that he has not given up looking for a solution.

I am wondering if 34C emulators for other platforms have this issue with the labels? Or did the original machine have this bug?

Love the app. Just wish there was a way to get a fix for this.



I am wondering if 34C emulators for other platforms have this issue with the labels?

With Nonpareil I can't reproduce that behavior. But maybe you can be more specific and post a small program that causes the trouble.

Kind regards



Hi Thomas,

Here's an example, taken from the HP-34C manual, page 112, which I post below. After keying in the program and rechecking the opcodes, I tried the examples at the bottom of the page and the calculator just launched into an endless loop.

Here it is:

LBL A, EEX, 4, X<>Y, X>Y, GTO B, 1 7 . 5, GTO 1, LBL B, 2 0,
LBL 1, %, RTN

Examples given in the book are:
15000 A should give a result of 3,000.00.

7500 A should give a result of 1,312.50.

Thanks for taking a look at this!

Edited: 27 Mar 2013, 11:40 p.m.


I can confirm the problem with this example. It appears to me that the GTO command has a bug: Sometimes it will just return to the first line but the next time it will just be ignored.

So if you run [GSB] [B] it will either end up in an endless loop or with 3.5 which is 20% of 17.5.

The following program works fine:


But when I add the command [x>y] beforehand and enter y = 10,000 and x = 7,500 so that the condition is not met the [GTO B] will be ignored but the [GTO 1] later as well!

I can hardly believe that this is a bug in the ROM of the HP-34C. Tons of people will have punched this program into their calculators. Maybe Eric Smith can have a look at that?





With go34c (android microcode emulator not based on non-pareil) the given program works nicely.

Either the rom of the emulator is corrupted or the cpu emulator still have some bugs in it.



Any plans to come out with an iOS version of go34c?

I'm currently using the iPhone/iPad app RPN-34C, which is otherwise great, except for the label search problem.


So this problem is not limited to just one platform? Could be that the developer of my app and yours got their code from the same source. Hope we can get a fix so we can realize the full power of this great calculator.


Program seems to work as expected on a real HP34C - I ran it a dozen or so times and got the same result each time..


Thanks so much Mike for trying it out on a physical HP-34C. So it appears that the label search problem is on some of the emulators, at least on Nonpareil and the iOS platforms. It is very frustrating as this is a very powerful calculator, but I can't have more than 2 labels in a program or the emulator gets confused.

Hope we can find a fix!

in San Francisco

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