The specific procedures as follows, I'm a little look not to understand, thank you ~ ~

/* set the stop bit */
The switch (stopbits)
{
Case 1:
Options. C_cflag & amp;=~ CSTOPB;
break;
Case 2:
Options. C_cflag |=CSTOPB;
break;
Default:
Fprintf (stderr, "Unsupported stop bits \ n");
Return (FALSE);
}