HP 12C Financial Calculator for iPhone

at a time--it's all there, and it all works. To make sure the programming worked, I tested some demo programs from my user's guide, and they all ran just fine.

Because the iPhone's CPU is much faster than the brain in the HP-12C calculator, the iPhone app's performance trounces that of the actual calculator. As a test, I gave my original calculator a huge amortization payment computation; it took about four seconds to come up with the answer after I tapped the PMT (payment) key. When I entered the same values into the iPhone version, the answer appeared literally as soon as I tapped the PMT key. Very nice. (Note that I don't know if newer models of the HP-12C have faster CPUs than does mine.)

Speaking of the keys; they darken when tapped, but as they're under your finger, that's sometimes hard to see. There's also a somewhat-too-loud (and not mutable without muting your iPhone) key click to let you know when you've pressed a key. This is an important feature, because not every key on the calculator changes the display. I do wish, however, that the volume of the click was user-controllable.

HP includes a user guide (tap the Menu button, which replaces the real version's On button), though it's an abbreviated version of the full guide. You won't find, for instance, the chapters on how to program the calculator, which is a shame. Creating simple programs to ease repetitive tasks is one of the best features on the HP-12C, but you really need the full manual to learn how to do it. HP even went so far as to replicate the data table that appears on the back of the physical calculator; tap the HP logo at the top corner of the screen to see it.

Because HP is using the original source for the iPhone version of the calculator, you don't get much benefit out of everything the iPhone has to offer. You can't copy and paste the results from the HP-12Cs display into another app. You can't use gestures, and there's no use of the larger screen to, for instance, display the values sitting on the stack (the stack holds previous results, making it easy to reuse them in future calculations).

So is the HP 12C Financial Calculator app worth $15? If you're an HP-12C user, or you're contemplating buying one, the answer is a resounding "yes." You'll be able to carry around one less device without giving up any of the physical calculator's capabilities. (And if you haven't bought your physical HP-12C yet, you'll save $55!) You won't gain a lot of new iPhone-specific features, but you will get a fully-functional digital representation of the physical device, and it will run many times faster than does the original.

HP 12C Financial Calculator is compatible with any iPhone or iPod touch running the iPhone 2.2 software update.

[Senior editor Rob Griffiths runs MacOSXHints.com.]