Interrupt 21h Function 440Dh Minor Code 6Bh

Unlocks the physical volume or decrements the lock level.

mov ax, 440Dh      ; generic IOCTL
mov bl, DriveNum   ; see below
mov ch, 08h        ; device category (must be 08h)
mov cl, 6Bh        ; Unlock Physical Volume
int 21h

jc enter

Parameters

DriveNum

Drive to unlock. This parameter must be one of the following values (same device unit numbers as for Interrupt 13h).

Value	Meaning
00 - 7Fh	Floppy disk drive (00 for the first floppy drive, 01 for the second, and so on).
80 - FFh	Hard disk drive (80 for the first hard disk drive, 81 for the second, and so on).

Return Values

Clears the carry flag if successful. Otherwise, the function sets the carry flag and sets the AX register to an error value.

Remarks

This function is used to release the lock obtained by using Lock Physical Volume (Interrupt 21h Function 440Dh Minor Code 4Bh). Only the lock owner can release the lock on a volume.

To release the lock on the volume, an application must call Unlock Physical Volume the same number of times that Lock Physical Volume was called.