Question

I used the system("pause") with stdio.h and it worked without error. When I looked at the stdio functions, system() is in stdlib. How come it worked, and here is the code?

#include <stdio.h>

int main() {
    printf("Hello World\n" );
    system("pause");
    return 0;
}

Answer 1

The answer is that it’s an implicit declaration. If the compiler doesn’t see a prototype for a function, it assumes it was declared like:

int system();

If you turn up the warning level on your compiler, you’ll likely see that this causes a warning. Implicit declarations are generally undesirable, but in this case it’s why this works without causing any errors.