ANONYMOUS wrote: Firstly, since the C99 standard (and hence in C11), main() must be a function returning an int, so you'll typically see: int main(void) or int main(int arc, char *argv[]); Within main() you can either return an integer value, or call the exit() function with an integer parameter. Of course the exit() function doesn't return, so you should only use it when you want the whole program to terminate at that point, and it shouldn't be used if main() should return to another function in the same program (rare). We should use EXIT_SUCCESS or EXIT_FAILURE in preference to 0 and 1 (so we don't have to remember what 0 means), but not all programs terminate with just a 0 or 1 exit status - see man zip, for example, which describes 19 different exit statues. More reading: [stackoverflow]⬈