RPN DEMO

Reverse Polish Notation (RPN) has been the preferred mode of operation of almost every HP calculator. It is also the mode of operation in the Forth and TIPI programming languages. RPN is also available as an option in the HP Calc program on the Palmtop.

If you've tried using RPN and have been confused by its way of doing calculations, then you might like to try RPNDEMO.

RPNDEMO is a freeware program from John Kennedy. It doesn't merely emulate an RPN calculator, it animates the operation in slow motion. When you key in a number and press Enter, you can watch previously entered numbers move up the X, Y, Z, T stack registers. When you perform a math operation, you can see the X and Y values pulled off the stack. You can also see where the LastX value comes from. The program allows keyboard entry of numbers and operations and it even lets you write programs that will automate the solution of complicated equations. The programming language is a subset of the language used in the HP 41C calculator.

If you're already familiar with RPN but would like to relive those glory days of the HP 41C or the HP 12C business calculator then you'll enjoy playing with RPNDEMO.

I tried the program on both a double speed Palmtop and a 100MHz desktop machine. Interestingly, the program works faster on the Palmtop: no kidding!

There is one nuisance feature. When you exit the RPNDEMO program, the cursor, at the DOS prompt, will have vanished. You can bring it back by Zooming the screen (Fn+Space) to the largest font size.

For more information about how to use RPN in the Palmtop's HP Calc program, see the Through The Looking Glass article in the May/June, 1994, issue of The HP Palmtop Paper. The same article can also be found on the CD InfoBase from Thaddeus Computing.