rpnjcalc manual

rpnjcalc is a RPN calculator implemented in javascript and html. It is platform independent and requires only a javascript capable webbrowser.

RPN stands for Reverse Polish Notation. Reverse Polish Notation was developed in 1920 by Jan Lukasiewicz as a way to write a mathematical expression without using parentheses and brackets.

Why should I use RPN?

RPN is something that you will have to learn but once you understood it and used it you will not use any other calculator anymore.

RPN became popular through the HP calculators and there is today a whole fan club around these HP calculators. Most HP calculators are collectors items and are sold for very high prices. See e.g http://www.hpmuseum.org/.

Unsing rpnjcalc

rpnjcalc is platform independent however the DOM/javascript standard complience is not the same in all browsers. rpnjcalc works with Mozilla, MS IE, Firebird and Opera. In Netscape 4 and Konqueror the pure calculator works but the keyboard interface does not work.

A very detailed explanation on how to use RPN can be found at: http://www.hpmuseum.org/rpn.htm.

In short: You use RPN just like you have been told in school when you manually resolved an equation on paper. You have the stack (LIFO, last in first out, registers: X, Y, A, B, C) to store intermediate results. Let's take an example.

      3 + 5
   16 - (2 * 6)
You could start to evaluate this term at the numerator but normally you would start with the more complex term, the denominator, in this case. This is also what you do on an RPN calculator:

Type: 2, enter, 6, *

You just calculated (2 * 6). Note that the numbers are entered first and then you say what to do with them (* = multiply). You see immediately the result in the display: 12

Continue with: 16, swap, -

You have just calculated: 16 - (2 * 6)=4. Now go to the numerator.

Type: 3, enter, 5 +

You have now calcualted 3+5 and you have result form the denominator (4) still in the stack at position Y.

Type: swap, /

... and you are done: The result is: 2

The specifics of rpnjcalc

You can either operate this calculator with mouse clicks or you can use the keyboard. However some web-browsers have keyboard shortcuts which may conflict with the keys used by this calculator. Therefore you need to place the mouse over the textarea below the calculator (click once, the field will become dark gray). The avaliable keyboard short cuts are documented in the textarea. Numbers and all basic mathematical operators are available as keyboard shortcuts.

More rarly used functions are only available as buttons (click with the mouse). This is also to avoid that the keyboard interface become too komplex to learn.

Function buttons:

Real HP RPN calculators

rpnjcalc is very nice for occasional calculations but it is nothing compared to a real HP calculator (such at the old HP15c, HP42, HP48...). The precision of those HP calculators is much higher than the mathematical precision that a web-browser offers. HP calculators are also programmable which is not the case for rpnjcalc.

Have fun with rpnjcalc but if you ever get the chance to buy a real HP then don't miss it. I have really fallen in love with my HP calculators and I still find the algebraic logic to be a bit lame. RPN is just a lot more elegant.

This rpnjcalc documentation was written by Guido Socher, guido at linuxfocus dot org, Copyright: GPL