Changeline flag. This bit is set to
1 if the device support determines that the media was removed since the
last I/O operation. To query whether the media has changed, call the device
driver Strategy Command "1h - MEDIA CHECK". (See "Physical Device Driver
Strategy Commands" in the Physical Device Driver Reference for more
information.)
If this bit is set to 0, then the physical device driver can return the
value 0, Unsure if media has changed, from the Media Check function.