Perhaps people are wondering why I keep writing so many flavors of my HP-12C Web emulator (most recent are for Android and iPhone).

HP-12C is kind of a gold standard for financial calculators, even though it shows its age. Some operations (e.g. depreciation) are seldom used, while it lacks important ones (e.g. Black-Scholes).

And let's be frank, the pocket calculator is a gadget whose usage tends assintotically to zero. It's like the wrist watch. Whoever wears one these days, think of it as jewerly, not as a time-keeping device.

But, in absolute numbers, the 12C still has a huge user base. Even my humble emulator gets something like 3000 hits a day. So it still pays off to develop some variations of the same theme.

I get some money for it via AdSense, but it obviously does not pay my bills; I see it more like points in a game. It is my pet project, most nerds have one and most nerds like to play with old architectures; I am not exception to the rule.

Obviously, I like the HP-12C calculator. I have three of them, all of them pretty worn out, to the point that I need to buy a fourth one soon. I also have an HP-11C (gift from a guy that liked the emulator). This one I seldom operate, it is handled as a sacred relic :)

My first HP-12C, bought in 1993, still in operation

This personal experience convinced me that emulator does not hurt HP sales. (If I change opinion in the future, I will take the emulator offline at once.) My current view is that such a software allows people to play with it, taking their time, and eventually they buy the real thing. After all, a physical calculator is much more convenient.

Another factor is trust: would you trust an emulator to calculate your mortgage? I'll tell you, I wrote the emulator, but I always resort to a real HP-12C when I have to handle some "serious" financial operation.

There is a sentimental reason for me to play with this gadget, perhaps is the most important one. Because of the HP-12C, and because I knew to operate it, I got my first "great" job -- that kind that pays a salary like your father's, and family begins to treat you like an human being instead of just another kid.

It happened this way: I wrote a Clipper system for factoring businesses. The manager of the biggest client called complaining that the system understimated the interest, which allegedly caused a sizable loss.

Facing an accusation like that, defense must be bold, even if the system was actually inacurrate, because there could be an implicit accusation of fraud. But I was pretty sure that there was no problem at all, since I employed the HP-12C formulas (that can be found in manual), and numbers tallied up with the calculator to the cent.

At meeting time, the conversation flowed as expected (meaning: myself in the role of culprit) until I unpocketed the HP to prove my point. The client's tone changed fast ("Do you actually know how to operate this? Hmmmm...").

We found that discrepancy was due to the fact that client's manager used a TI calculator (and used the financial functions in interesting ways).

To please him, I changed the system in loco to mimic his calculation, which reinforced the good impression I made. One week after, I was hired full-time in there.

Being a generalist is demodé (indeed it is not ideal) but it is funny how the possession of a knowledge completely unrelated with IT actually put my carreer on track.