btw, a silly question - which way do you include it?
#include "stdio.h", or
#include <stdio.h> ?
(note angle brackets vs quotation marks)
<stdio.h> searches in standard C library locations, whereas "stdio.h" searches in the current directory as well.
Ideally, you would use <...> for standard C libraries and "..." for libraries that you write, and are present in the current directory.