DPB (FAT32)

[Windows 95 only.]

The DPB was extended to include FAT32 information. Changes are effective for Windows 95 OEM Service Release 2 and later.

DPB STRUC
    dpb_drive            DB    ?
    dpb_unit             DB    ?
    dpb_sector_size      DW    ?
    dpb_cluster_mask     DB    ?
    dpb_cluster_shift    DB    ?
    dpb_first_fat        DW    ?
    dpb_fat_count        DB    ?
    dpb_root_entries     DW    ?
    dpb_first_sector     DW    ?
    dpb_max_cluster      DW    ?
    dpb_fat_size         DW    ?
    dpb_dir_sector       DW    ?
    dpb_reserved2        DD    ?
    dpb_media            DB    ?
ifdef NOTFAT32
    dpb_first_access     DB    ?
else
    dpb_reserved         DB    ?
endif
    dpb_reserved3        DD    ?
    dpb_next_free        DW    ?
    dpb_free_cnt         DW    ?
ifndef NOTFAT32
    extdpb_free_cnt_hi   DW    ?
    extdpb_flags         DW    ?
    extdpb_FSInfoSec     DW    ?
    extdpb_BkUpBootSec   DW    ?
    extdpb_first_sector  DD    ?
    extdpb_max_cluster   DD    ?
    extdpb_fat_size      DD    ?
    extdpb_root_clus     DD    ?
    extdpb_next_free     DD    ?
endif
DPB ENDS

Members

dpb_drive

The drive number (0 = A, 1 = B, and so on).

dpb_unit

Specifies the unit number. The device driver uses the unit number to distinguish the specified drive from the other drives it supports.

dpb_sector_size

The size of each sector, in bytes.

dpb_cluster_mask

The number of sectors per cluster minus 1.

dpb_cluster_shift

The number of sectors per cluster, expressed as a power of 2.

dpb_first_fat

The sector number of the first sector containing the file allocation table (FAT).

dpb_fat_count

The number of FATs on the drive.

dpb_root_entries

The number of entries in the root directory.

dpb_first_sector

The sector number of the first sector in the first cluster.

dpb_max_cluster

The number of clusters on the drive plus 1. This field is undefined for FAT32 drives.

dpb_fat_size

The number of sectors occupied by each FAT. The value of zero indicates a FAT32 drive. Use the value in extdpb_fat_size instead.

dpb_dir_sector

The sector number of the first sector containing the root directory. This field is undefined for FAT32 drives.

dpb_reserved2

Reserved field. Do not use.

dpb_media

Specifies the media descriptor for the medium in the specified drive.

reserved

Reserved field. Do not use.

dpb_first_access

Indicates whether the medium in the drive has been accessed. This field is initialized to -1 to force a media check the first time this DPB is used.

dpb_reserved3

Reserved field. Do not use.

dpb_next_free

The cluster number of the most recently allocated cluster.

dpb_free_cnt

The number of free clusters on the medium. This field is 0FFFFh if the number is unknown.

extdpb_free_cnt_hi

The high word of free count.

extdpb_flags

Flags describing the drive. The low 4 bits of this field contain the 0-based FAT number of the Active FAT. This field can contain a combination of the following values.

Value	Description
BGBPB_F_ActiveFATMsk (000Fh)	Mask for low four bits.
BGBPB_F_NoFATMirror (0080h)	Do not Mirror active FAT to inactive FATs.

Bits 4-6 and 8-15 are reserved.

extdpb_FSInfoSec

The sector number of the file system information sector. This field is set to 0FFFFh if there is no FSINFO sector. Otherwise, this value must be non-zero and less than the reserved sector count.

extdpb_BkUpBootSec

The sector number of the backup boot sector. This field is set to 0FFFFh if there is no backup boot sector. Otherwise, this value must be non-zero and less than the reserved sector count.

extdpb_first_sector

The first sector of the first cluster.

extdpb_max_cluster

The number of clusters on the drive plus 1.

extdpb_fat_size

The number of sectors occupied by the FAT.

extdpb_root_clus

The cluster number of the first cluster in the root directory.

extdpb_next_free

The number of the cluster that was most recently allocated.