RPN Memory Calculator

RPN Memory Calculator is a simple to use reverse polish notation calculator with seven functions and memory operations including a memory value display and three visible registers. This is not intended to be a full scientific function calculator, it is a handy implementation of basic calculator operations using RPN.
The calculator also integrates unit conversions, so you can convert the value in the x register. This allows you to choose a type (Speed, Mass, Temperature, Pressure etc) and then pick a from and to type. The converted number can either be accepted back into the x register, or discarded.
The calculator remembers state so that calculations you have been working on, with results stored in either the memory field or any of the registers, will still be present when re-open the app any time in the future. All registers, even the hidden ones above z are stored.