PCalc is ideal for scientists, engineers, students, programmers, or indeed anybody looking for a feature rich calculator. It includes an optional RPN mode and multi-line display, a choice of button layouts, an extensive set of unit conversions, a paper tape, multiple undo and redo, engineering and scientific notation, as well as support for hexadecimal, octal, and binary calculations.
The latest update also adds support for external Bluetooth keyboards. PCalc and PCalc Lite are available from the App Store.