Question

I was implementing a small cmd calculator in Objective-C for OOP practice. I was getting input for doubles via scanf() and to get the input, I used %f for formatting then put it in a double variable. For some reason it would always read the input odd. I don’t know what was going on but when I changed all of the types to int, it worked out perfectly.

Answer 1

The scanf() format for double is "%lf".

printf() can use the same "%f" format for both float and double, because float arguments to variadic functions are promoted to double. There’s no such promotion for scanf() because you’re passing a pointer, and you need to have an actual float or double object in memory.