_PHATVBR Struct Reference
[Volume Support]

#include <phatvol.h>

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Detailed Description

Volume boot record.

Data Fields
u_char	boot_jump [3]
	Jump instruction, contains E9xxxx or EBxx90.
u_char	boot_oem [8]
	OEM name and version.
u_short	bios_sectsz
	Bytes per sector.
u_char	bios_clustsz
	Sectors per cluster.
u_short	bios_rsvd_sects
	Number of reserved sectors.
u_char	bios_ntabs
	Number of allocation tables.
u_short	bios_rootsz
	Number of root directory entries.
u_short	bios_volsz
	Total number of sectors.
u_char	bios_media
	Media descriptor.
u_short	bios_tabsz
	Number of sectors per allocation table.
u_short	bios_sects_p_trk
	Number of sectors per track.
u_short	bios_heads
	Number of heads.
u_long	bios_sects_hidd
	Number of hidden sectors.
u_long	bios_volsz_big
	Total number of sectors for huge drives.
u_long	bios_tabsz_big
	Number of sectors per allocation table for huge drives.
u_short	bios_xflags
	Extended flags.
u_short	bios_fsver
	File system version.
u_long	bios_root_clust
	First cluster of root directory.
u_short	bios_fsinfo
	File system info sector.
u_short	bios_boot_bak
	Boot backup sector.
u_char	bios_rsvd32 [12]
	Reserved for future expansion.
u_char	boot_drive
	Logical drive number.
u_char	boot_rsvd_nt
	Reserved field, used by Windows NT.
u_char	boot_xsig
	Extended signature.
u_long	boot_vol_id
	Volume serial number.
u_char	boot_vol_lbl [11]
	Volume label.
u_char	boot_vol_fs [8]
	File system.

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Field Documentation

u_short _PHATVBR::bios_sectsz

Bytes per sector. The BIOS parameter block starts here.

u_short _PHATVBR::bios_rsvd_sects

Number of reserved sectors. This includes the boot sector, which is typically the only reserved sector with PHAT12/16.

u_short _PHATVBR::bios_tabsz

Number of sectors per allocation table. If zero, then the value is stored in bios_tabsz_big.

u_long _PHATVBR::bios_sects_hidd

Number of hidden sectors. With PHAT12 this field is two bytes only. We ignore it anyway.

u_long _PHATVBR::bios_volsz_big

Total number of sectors for huge drives. Valid only if the value in bios_volsz is zero.

u_long _PHATVBR::bios_tabsz_big

Number of sectors per allocation table for huge drives. This and the following 6 fields are available with PHAT32 only.

u_short _PHATVBR::bios_xflags

Extended flags. If bit 7 is set, then bits 0-3 specify the active allocation table. This feature is not yet supported. PHAT32 always updates the first two tables.

u_char _PHATVBR::bios_rsvd32[12]

Reserved for future expansion. End of the BIOS parameter block.

u_char _PHATVBR::boot_drive

Logical drive number. With PHAT12 and PHAT16 this and the following fields are at offset 36.

u_char _PHATVBR::boot_xsig

Extended signature. If 0x28 or 0x29, than the following fields are valid.

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