Maybe I should leave well enough alone, but I want to give my 2 cents about HP's. They blow!. Compared to TI's and Casio's they're not very user-friendly
That infernal RPN is ridiculous. Having been a surveyor, the HP-48GX was the tool to use in the field. It was the most popular until the advent of the IPac.
It was a good data collector, but very susceptible to 'throwing fits' as I called it. I had many an instance of 'locking up' and losing data out of the blue. I hated them, but they were the tool used at the time.
As for being a general calculator, they do not compare to TI's.
The HP-48GX had a software card manufactured by SMI which enabled a surveyor to perform many operations(traversing, resections, data collection, etc.). One simply plugged the card into one of the ports in the back and used it as a surveying pac.
This may be childish to admit, but over time I had managed to acquire some programs which I entered manually that did not utilize the card. Needless to say, about half way through entering in the quite lengthy programs, the calculator 'took a dump' and erased my time-consuming efforts. You know what happened to that calculator?. I bruised my heel on it.
I also have a Casio for which I wrote many a trig-oriented surveying program which has never given a problem(inverse, azimuth-to-azimuth, side shot, etc.)
The only thing HP's are good for, in my opinion, is that the old ones are quite the collector's item these days.