For iPad and iPhone users, RPN-45 HD and RPN-45 SD, respectively have been updated. The update improved the y^x function and made the display compatible with how most other HP calculators switched from FIX to SCI mode. For the iPad version, additional backgrounds have been added.
Thanks, Willy, for a nice update!
Bob
I have the RPN-67 Free application by the same author. It's very faithful to the original (I had a real one, bought long ago), except the free version of the application isn't programmable.
I really liked the HP-67, the last of what I call the HP Battleship class. One of the engineers must have had fat fingers like me and so allowed for generous inter-key spacing. The display was superior to any which Texas Instruments offered at the time; it supported a full ten digits of mantissa, two digits of exponent, signs for both, and the radix point got its own slot. My only complaint is that the keypad's printed legends started to fade after years of heavy usage.
I love the HP LED calculators. There's something wonderful about them. If you can't get the originals, all of the emulators from Cuvee software are first rate. The newest offering emulates the HP-97 which must be really nice. Currently I have the original iPad which won't support it.