There was a time when every physics and engineering student aspired to own a Hewlett-Packard calculator. The calculators that HP "makes" today are a pale shadow of the great calculators that they made in the past. Well, they still make the 12C for the finance, but the scientific calculators aren't as good. The current scientific calculators from HP can switch between algebraic and RPN modes. I like my HP50G, but it doesn't have the robust presence of the 15C (I currently own a Limited Edition from a limited run a few years ago. The Limited Edition feels like the original but is much faster. Since 2003 HP calculator design has been outsourced to Kinpo Electronics and the division responsible for the great calculators of the past has long since disappeared. I don't use most of the features of my 50G - I use a computer instead. But the HP15C is the perfect scientific calculator.
Until recently, I kept my 15C at home as it was irreplaceable. Not anymore SwissMicros is making an excellent clone. They have had the DM15 for a while, but it was credit card sized. The DM15L is the same size and works just like my limited edition. So if you don't have an HP RPN scientific calculator you can get one - and it is a copy of the best one that was ever made. There are other RPN calculators on the page that clone other HP RPN calculators.
Never used an RPN calculator - its probably best not to start - once you've learned how to use one, you will never want to go back to a regular calculator. I have HP15C emulators on my iPhone and on all my computers. If you want to try one, you might want to download this simulator. Don't blame me if you discover the need to own a physical model - but at least you know where to find one!
