Which HP-41CX app would you recommend?
The one I have is i41CX+
Now that I look at it closely, it appears that this particular one is only available for Apple products.
In any event, I’ve had for about three years, and while there were a few bugs at first, periodic well-constructed updates have resulted in it running pretty much flawlessly. It really is a remarkable app.
The phone screen simulates the look of the original, and since the width and length (but fortunately not the thickness) of my iPhone 8 are similar to the dimensions of an HP-41C, the scale and spacing of the “buttons” is quite similar to the real thing. It even has a setting that provides a “click” with each keystroke, just like a brand new 41c.
PS - there is also a very nice HP-42S emulator called Free 42. As its name implies, it is free,so it’s got that going for it. It is also definitely available for non-Apple devices.
I don’t know how familiar you are with the 42S but it was released during the mid-1980s as a sort of updated but simplified versions of the 41C. It has essentially the same basic capabilities as the 41C but does not have any plug-in modules. It does have a good deal more memory than the older calculator. It also has a two-line display. It’s a pretty powerful scientific programmable calculator, and it’s programming “language” is essentially identical to that of the 41C.
As with the 41CX emulator, it was a little buggy on initial release, but it’s been around a couple of years, and the developer appears dedicated to eliminating an/all bugs and quirks. I get an update about once a week, and they are worthwhile. As of now, ‘Free 42’ works almost as well as i41CX+.