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