AL output status code (if no error)
Info: This function checks to see if a device is ready to receive
If the handle is a disk file:
AL always returns with ffH (ready) even if the disk is full or
no diskette is present etc.
If the handle is a device:
AL=00H the device is not ready
AL=ffH the device is ready (output will be accepted)
Notes: This fn makes for a simple way to determine if an output
device, such as a COM port, is ready to accept output. It is
not useful for disk files.
Fn 4406H (Query Handle Input Status)