function cast?

(sorry for my first uncomplete email, please abandon the first mail)

Hi All,

Sometimes i see codes are written like this:

(void) printf(fmt);

- or -

(void) close(fd);

What these means? i think it is not necessary to put that 'void' on a
statement, or it just like when we cast a data type like:

double d = 93.43;
int i = (int) d;

but why those function need to be casted in a 'void' ?

Thanks,