This calculator uses postfix notation also known as Reverse Polish Notation (RPN). The advantage of this method over traditional calculators is that you can compute 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 in the lower
right corner as this avoids the browsers keyboard shortcuts to
take effect.

rpnjcalc was written by Guido Socher, guido at linuxfocus dot org, Copyright: GPL, Version: 1.2