Int 21 Fn 6C00  - Dos 4.0+ - Extended Open/create                          [D]

   AX = 6C00h
   BL = open mode as in AL for normal open (see also AH=3Dh)
       bit 7: inheritance
       bits 4-6: sharing mode
       bit 3 reserved
       bits 0-2: access mode
       100 read-only, do not modify file's last-access time (DOS 7.0)
   BH = flags
       bit 6 = auto commit on every write (see also AH=68h)
       bit 5 = return error rather than doing INT 24h
       bit 4 = (FAT32) extended size (>= 2GB)
   CX = create attribute (see #1458)
   DL = action if file exists/does not exist (see #1459)
   DH = 00h (reserved)
   DS:SI -> ASCIZ file name

Return: CF set on error
      AX = error code (see #1366 at AH=59h/BX=0000h)
   CF clear if successful
      AX = file handle
      CX = status (see #1457)

Notes: the PC LAN Program only supports existence actions (in DL) of 01h,
     10h with sharing=compatibility, and 12h
   DR DOS reportedly does not support this function and does not return
     an "invalid function call" error when this function is used.
   the documented bits of BX are stored in the SFT when the file is opened
     (see #1327,#1328)
BUG:   this function has bugs (at least in DOS 5.0 and 6.2) when used with
     drives handled via the network redirector (INT 2F/AX=112Eh):
       - CX (attribute) is not passed to the redirector if DL=11h,
       - CX does not return the status, it is returned unchanged because
         DOS does a PUSH CX/POP CX when calling the redirector.

See Also: AH=3Ch,AH=3Dh,AX=6C01h,AX=7160h/CL=00h,INT 2F/AX=112Eh

(Table 1457)
Values for extended open function status:
 01h   file opened
 02h   file created
 03h   file replaced

Bitfields for file create attribute:
Bit(s) Description (Table 1458)
 6-15  reserved
 5 archive
 4 reserved
 3 volume label
 2 system
 1 hidden
 0 readonly

Bitfields for action:
Bit(s) Description (Table 1459)
 7-4   action if file does not exist
   0000 fail
   0001 create
 3-0   action if file exists
   0000 fail
   0001 open
   0010 replace/open