How to use \a for audible bell?

Question

Which header file is used?

Answer 1

The header file that contain functions that prints to an output stream (like stderr or stdout), you need to #include <stdio.h>

Then try
printf("\a");

You should hear an alert sound! :-)
If you don't, it could be because your operating system sounds are disabled or configured in such a way that no sound is audible.