my reference point are HP calculators, and a never dying dream is to port nonpareil to whatever platform I have in my pocket. but 'nonpareil' is written in C, and I'm not yet sure how to compile C sources on N9. The calculator you want, that's probably the 12c, a machine still in commerce, some 35 years after its introduction. if I have the C core compiled, attaching a user interface to it is not the hardest task.