This calculator uses postfix notation also known as Reverse Polish Notation (RPN). This notation has many advantages over Algebraic notation. One advantage is that you can calculate even complicated terms without braces.

An example: Suppose you want calculate 5 * (3 + 4)

Press the following keys on the calculator: 5, enter, 3,
enter. The 3 and 5 did go into the calculator's memory, the
stack. Now you type 4 and press + to add. After this you just
press * to multiply.

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 text area below
as this avoids the browsers keyboard shortcuts to take
effect. The keyboard interface was tested with Mozilla, MS IE and Opera.
It does not work with Netscape 4.

rpnjcalc comes with a small manual which you can find here: rpnjcalc-help-0.1.html

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