Int 21 Fn 69  U - Dos 4.0+ Internal - Get/set Disk Serial Number           [D]

   AH = 69h
   AL = subfunction
       00h get serial number
       01h set serial number
   BL = drive (0=default, 1=A, 2=B, etc)
   BH = info level (00h only for DOS; OS/2 allows other levels)
   DS:DX -> disk info (see #1455)

Return: CF set on error
       AX = error code (see #1366 at AH=59h/BX=0000h)
   CF clear if successful
       AX destroyed
       (AL = 00h) buffer filled with appropriate values from extended BPB
       (AL = 01h) extended BPB on disk set to values from buffer

Notes: does not generate a critical error; all errors are returned in AX
   error 0005h given if no extended BPB on disk
   does not work on network drives (error 0001h)
   buffer after first two bytes is exact copy of bytes 27h thru 3Dh of
     extended BPB on disk
   this function is supported under Novell NetWare versions 2.0A through
     3.11; the returned serial number is the one a DIR would display,
     the volume label is the NetWare volume label, and the file system
     is set to "FAT16".
   this function is not supported by Novell DOS 7 through Update 13, but
     Personal NetWare 1.0 and Update 15 do support this function
   the serial number is computed from the current date and time when the
     disk is created; the first part is the sum of the seconds/hundredths
     and month/day, the second part is the sum of the hours/minutes and
     year
   the volume label which is read or set is the one stored in the extended
     BPB on disks formatted with DOS 4.0+, rather than the special root
     directory entry used by the DIR command in COMMAND.COM (use AH=11h
     to find that volume label)

See Also: AX=440Dh"DOS 3.2+"

Format of disk info:
Offset Size    Description (Table 1455)
 00h   WORD    0000h (info level)
 02h   DWORD   disk serial number (binary)
 06h 11 BYTEs  volume label or "NO NAME    " if none present
 11h  8 BYTEs  (AL=00h only) filesystem type (see #1456)

Note:  under MS-DOS 7.0 or a Windows95 DOS box, the volume label field can be
     all blanks even when a volume label has been set (the Win95
     installation seems to blank the volume label field in the partition
     boot sector; once LABEL has been run, the volume label is reported
     correctly)

See Also: AH=4Eh

(Table 1456)
Values for filesystem type:
 "FAT12      " 12-bit FAT
 "FAT16      " 16-bit FAT
 "CDROM      " High-Sierra CD-ROM filesystem
 "CD001      " ISO 9660 CD-ROM filesystem
 "CDAUDIO "    audio CD

See Also: #1455