The RPN notation has many advantages over the Algebraic notation in terms of speed and usability. 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 bottom display area (X). The keyboard interface was tested with Firefox, Mozilla, MS IE and Opera. It does not work with Netscape 4.
The following keyboard short cuts are defined:
c=+/-, C=clear, s=swap, p=Roll Stack
-=subtract (use c to change the sign)
For all other operations just use the mouse and calculator keypad.