CompiledMonkey,
have you learned about classes yet? If so, or when you do, you can make the calculator object oriented.
P.S.:I attached my first calculator here. Before you look at the source try adding a square root function. I didn't get to this, but you could also add powers. If you're stumped, you can use sqrt() or pwr() in math.h (or is the newer one cmath or math?)
