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 physical device driver Strategy Command "1h - MEDIA CHECK". (Refer to
"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.
Bit 2