Category: DOS kernel
INT 21 - 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 SeeAlso: AX=440Dh"DOS 3.2+",AX=440Dh/CX=084Bh,AX=440Dh/CX=086Ah SeeAlso: AX=440Dh/CX=086Ch