Int 21/AX=440Dh/CX=084Ah

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MS-DOS 7.0+ - GENERIC IOCTL - LOCK LOGICAL VOLUME

AX = 440Dh
CX = 084Ah / 484Ah
(category code 08h for FAT12/16, 48h for FAT32; minor code 4Ah)
BL = drive number (01h=A:,02h=B:,etc)
BH = lock level (00h-04h)
DX = drive permissions (see #01575) for Level 1 lock or second
Level 0 lock when formatting

Return:
CF set on error AX = error code (01h,02h,etc.) (see #01680 at AH=59h/BX=0000h) CF clear if successful

Notes: The logical volume must be locked before direct disk accesses are permitted by Windows95/98. The commandline LOCK issues a level 4 lock. Windows98 only permits lock levels 0 and 4

BUG: Windows98 will return an error (invalid function) if the specified drive number is zero or more than 32, but only allocated 26 bytes for recording locks, so BL=1Bh..20h will trash internal data structures

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 01575) 0 allow writes 1 disallow new file mappings 2 volume locked for formatting

Category: DOS Kernel - Int 21h - M

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