Hi,
the DDT defined in device.h differs from that used by MS-DOS for FAT32.
(Applicable to MS-DOS 7.10+ only.) MS-DOS includes the 12 reserved FAT32
BPB bytes in the BPBs contained within the DDT. MS-DOS also removes the 6
reserved bytes behind the second BPB in the DDT. The ddt_flags field is
set to 20h by MS-DOS for FAT32 partitions, but I think that's less
important than the layout and size difference. Here's a correction:
...
bpb ddt_bpb; /* BIOS Parameter Block */
#ifdef WITHFAT32
UBYTE ddt_bpbreserved[12]; /* part of FAT32 BPB above */
#endif
UBYTE ddt_flags;
/* bit 5: 32-bit FAT
bit 6: 16-bit FAT (else 12-bit FAT)
bit 7: unsupportable disk (all accesses will return Not Ready) */
UWORD ddt_FileOC; /* Count of Open files on Drv */
UBYTE ddt_type; /* device type */
UWORD ddt_descflags; /* bit flags describing drive */
UWORD ddt_ncyl; /* number of cylinders
(for partition only, if hard disk) */
bpb ddt_defbpb; /* BPB for default (highest) capacity
supported */
#ifdef WITHFAT32
UBYTE ddt_defbpbreserved[12]; /* part of FAT32 BPB above */
#else
UBYTE ddt_reserved[6]; /* (part of BPB above) */
#endif
...
Regards,
Christian
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