bcRPN

This is a RPN (Reverse Polish Notation) Calculator.  It supports complex numbers and uses extended precision math for all operations.  The stack depth is unlimited.  In case a mistake was made, up to 10 operations can be undone.

RPN calculators work by entering the numbers on the stack first, then selecting the operation.  For example to add 3 + 4, press:
3
Enter
4
+