MPCalcRB is a multi-precision RPN calculator built using REALbasicand the developer's MPCalc plugin.

MPCalcRB can be used on Windows, Mac OS X and Linux.

It can handle numbers with up to 30,000 digits. It can also handle numbers whose absolute values lie between about 10^-40000000 and 10^+40000000. The popup menu selects from three keypads. There are keyboard equivalents for the functions. Over forty scientific functions are now available.

RPN stands for Reverse Polish Notation. Like a Hewlett-Packard RPN handheld calculator, MPCalcRB has seven registers in its stack (think of the seven registers arranged vertically with the display textbox at the bottom) and should behave like an HP calculator. Start up the application "MPCalcRB" in any way you prefer. On the left are buttons corresponding to some of the keys on a handheld RPN calculator.

In the middle are the number buttons and the command buttons, /, *. -, +. On the right the textbox corresponds to a handheld's display. The number buttons on your keyboard are also active. If you have a keypad those keys are also active. The /, *. -, + keys correspond to the /, *. -, + buttons. We'll proceed by example. Do exactly as indicated. It is best not to click in the textbox unless you need to correct an input. You can use the back arrow button or the Delete key to correct your own input. The 'clr' button zeroes the current entry, not all the registers in the stack.