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

   AX = 440Dh
   CX = 084Ah (category code 08h, minor code 4Ah)
   BL = drive number (00h=default,01h=A:,etc)
   BH = lock level (00h-04h)
   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

Notes: the logical volume must be locked before direct disk accesses are
     permitted by Windows95
   the commandline LOCK issues a level 4 lock

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

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

Bitfields for drive permissions:
Bit(s) Description (Table 1262)
 0 allow writes
 1 disallow new file mappings
 2 volume locked for formatting