Int 21 Fn 440D  - Ms-dos 7.0 - Generic Ioctl - Lock Physical Volume        [D]

   AX = 440Dh
   CX = 084Bh (category code 08h, minor code 4Bh)
   BL = physical drive number (00h-7Fh = floppy, 80h-FFh = hard disk)
   BH = lock level (00h-03h)
   DX = drive permissions (see #1262) for Level 1 lock or second
       Level 0 lock when formatting

Return: CF set on error
       AX = error code (01h,02h,etc.) (see #1366 at AH=59h/BX=0000h)
   CF clear if successful

Note:  the physical volume must be locked before direct disk writes via
     INT 13 are permitted by Windows95

See Also: AX=440Dh"DOS 3.2+",AX=440Dh/CX=084Ah,AX=440Dh/CX=086Bh

See Also: AX=440Dh/CX=086Ch