Special Considerations for MS- DOS – Based Applications

MS-DOS – based applications may directly call the volume-locking IOCTL functions by using Interrupt 21h, as described in the reference material.

When a windowed MS-DOS – based application obtains a level 3 lock, the system forces it to full screen mode to avoid deadlock with the display driver. When the application releases the level 3 lock, it remains in full screen mode.

Applications must not call the Advanced SCSI Programming Interface (ASPI) functions inside a level 3 lock. These functions bypass the file system, leaving it in an inconsistent state.

When MS-DOS – based applications run in single MS-DOS application mode (real mode), they may issue the volume-locking IOCTL functions and the functions will succeed. However, because there is no multitasking, there is only one lock rather than a hierarchy as when Windows 95/98 is running. The volume-locking IOCTL functions will fail on down-level versions of MS-DOS.