What does the include in the middle of code in C?

Question

Please, could you tell me what does the code below do?

...code...
#include file.h
...code...

I was used to put includes a the beggining of

Answer 1

It's usage is not limited to the starting of the file, but note that the variables, macros or functions declared in this header will not be usable before the include statement even if on the same file.