Touch RPN (formerly known as Touch Fin) is a financial and scientific calculator for iPhone. It implements most features of the industry-standard HP-12C calculator, including programming functions.
The calculator mimics the real device as closely as practically possible, including details such as rounding up of n in financial calculations. It shares the same limitations of a real 12C: only 99 programming steps, 20 memory positions, etc.
To open the new Settings pane, press the ON button, then "Settings" at the right top corner, to access the preferences panel.