My former telephone died and my wife got me an iPhone 5. Then I set to get some calculators to work with in the system. In particular, I downloaded all the free ones. Here's what I got:
I did not load the HP15c in any of its versions, since i always carry one with me. I find that it is the finest device ever made for personal calculations, only rivaled by the mighty HP42s - but this is a completely different discussion...
I took the free version of the HP42s, Free42. It is built for the smaller screen of the previous iPhone versions
I got RPN25 calc. When you need a simple, RPN calculator, this is a nice alternative, since there are not too many keys and it has the basic set of functions. Also for smaller screens, but it is a pleasure to use.
I got a very simple RPN calc, iRPN Calc, which is as simple a calculator as you may find anywhere, with a very nice twist: you can change the items in the stack by moving them around with your fingers. Also for smaller screen.
I48. not built for the iPhone 5 - there is a wide white band in the lower part of the screen - it is in need of an adaption or at least a recompiling, in order to be livable with in the iPhone 5.
PowerOne SL: does not try to mimic the original HP calculators, and it is the first one that does fill the whole screen. It opens as an algebraic model, but when going to the settings page, you can change it into RPN. It has several pages for different functions, from numbers, angle functions, other transcendental functions, and memory registers. This is a fine addition to the screen.
One of the calculators that has marked my scientific life was the HP41cv. This was a machine that offered a young engineer the promise of doing anything - from controlling peripherals to all kinds of calculators. I have been following with attention the HP41cl developments, and I find extremely interesting the old, loved 41c body with throughly modern innards - and sometime I will get one. But it just does not fit in my pocket.
Therefore I took the plunge and download the full version i41CX+, with CAS. Let me state first that I have not been able to delve into the CAS, since I have been exploring the different modules available (the CAS is one of them). It works basically as the original one, and it has been adapted to the longer screen of the iPhone 5. Lest I forget, it is not free, but close to 25 € (once bought, you cannot see the price in the store). Let me say that it fully justifies the purchase.