r.Calc vs Plus42

This classic RPN (Reverse Polish Notation) calculator is a simple calculator for daily uses. The calculator features a four visible level stack, the total stack size has a total of hundred positions. A progress bar on the top of the screen shows you how the stack is full. For now the implemented operations are; Plus, Minus, Multiply, Divide, Opposite, Inverse. Other facilities like swap the first two number in the stack and recall from the last operation the two arguments should simplify the life. All keyboard errors are notified by a vibration.

Plus42 is an advanced scientific programmable calculator, based on Free42. Free42, in turn, is a complete re-implementation of the HP-42S scientific programmable RPN calculator, which was made from 1988 until 1995 by Hewlett-Packard. Free42 is a complete rewrite and contains no HP code whatsoever. Plus42 builds on Free42 and adds: Algebraic expressions modeled after those used on the HP-27S and HP-17B/19B; attached units and unit conversions modeled after those used on the HP-48/49/50 series; directories for more organized storage of programs and variables; a larger display, with 8 rows and 22 columns (131x64 pixels) by default, which the user may resize at will; time value of money and amortization schedules; and two-dimensional plotting of functions, with ability to zoom and pan, and find integrals and roots from points in the plot.