Orpie is a fullscreen RPN calculator for the console. Its operation is similar to that of modern HP calculators, but data entry has been optimized for efficiency on a PC keyboard. Features include:

* real and complex numbers and matrices * extensive function library * command completion of function names * base conversions * units and conversion factor handling * exact integer arithmetic, with unlimited integer size * visible stack, with browsing/modification capability * user-defined variables * user-configurable keybindings, via a Mutt-like rcfile * context-sensitive help