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Format of Extended BIOS Parameter Block

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Offset Size Description

00h

25 BYTEs

same as standard DOS 4-6 BPB (see #01663)

19h

DWORD

sectors per FAT if WORD at 0Bh is 0000h

1Dh

WORD

extended flags
bit 7 : do not mirror active FAT to inactive FATs
bits 6 - 4 : reserved (0)
bits 3 - 0 : the 0-based FAT number of the active FAT (if mirroring disabled)

1Fh

WORD

file system version
high byte = major
low byte = minor
0000h = Win95-OSR2

21h

DWORD

starting cluster number of root directory

25h

WORD

file system information sector number (see also #01788)
FFFFh if none

27h

WORD

sector number of backup boot sector (FFFFh if none)

29h

6 WORDs

reserved

See Also:

#01560,#01787