C prototype functions

Question

As a beginner to C, I can understand the need for function prototypes in the file, but am unsure of a couple things.

First, does every function call outside of the m

Answer 1

Others have already pointed out that C doesn't require prototypes for functions. I'll just add a couple minor points.

First of all, without a prototype, the arguments to a function always undergo "default promotions" before being passed as parameters, so (for example) all the smaller integer types get promoted to int, and float gets promoted to double. Therefore, without a prototype, it's impossible for a function to receive (for example) a char, short, or float. If the function is defined to receive one of those types, there will be a mismatch between what's passed and what the function expects, giving undefined behavior (any other mismatch gives undefined behavior as well).

Second, if a function is defined with a variable argument list, then you do need a prototype for it, or else calling it will result in undefined behavior.