Understanding function declarations

For the compiler to recognize a function call when it sees it, it must already know about the function. In other words, it must process the function statement's definition before it can process the call to that function. We have seen this behavior in all of our programs up to this point. In each program, we have defined the function and then, later in our program, called it.

This behavior is somewhat limiting since we may want to call a function from anywhere in our program. We don't want to get caught up in its relative position in the program and have to reshuffle the definitions of the functions just to make the compiler happy. The compiler is supposed to work for us, not the other way around.

C provides a way to declare a function so that the compiler knows just enough about the function to be able to process a call to the function before it processes the function definition. These are called function declarations...