How to correctly use the extern keyword in C

Question

My question is about when a function should be referenced with the extern keyword in C.

I am failing to see when this should be used in practice. As I

Answer 1

A very good article that I came about the extern keyword, along with the examples: http://www.geeksforgeeks.org/understanding-extern-keyword-in-c/

Though I do not agree that using extern in function declarations is redundant. This is supposed to be a compiler setting. So I recommend using the extern in the function declarations when it is needed.