It's possible to design a calculator with simple interface and basic functionality.
Although, have you thought about what makes default calculators from companies such as Microsoft and Apple stand-out from the rest.
I would not jump into technical jargon and state it simply. BODMAS rule of maths is one of the first things we learnt in elementary school. Keeping in mind, the precedeny rules and how to make computer understand what is meant is what the money is what will make me stand out from the rest.
It's now your choice whether you want a basic calculator with basic facilities or a calculator which most of the time understands what you mean.
Thank you!