1 more doubt !

[S.Tobias]

No version of the C standard requires anything inside the parentheses
in the definition of a function accepting no arguments. This is
perfectly legal even in C99.

[snip]

According to the standard (C99 5.1.2.2.1p1), only the following
two definitions of main are guaranteed to be valid:

int main(void) { /* ... */ }
int main(int argc, char *argv[]) { /* ... */ }

.... "or equivalent" (same paragraph).

`int main(void) {}' and `int main() {}' definitions are equivalent.