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Format of BIOS Parameter Block

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Offset Size Description

00h

WORD

number of bytes per sector

02h

BYTE

number of sectors per cluster

03h

WORD

number of reserved sectors at start of disk

05h

BYTE

number of FATs

06h

WORD

number of entries in root directory

08h

WORD

total number of sectors
for DOS 4.0+, set to zero if partition >32M, then set DWORD at 15h to actual number of sectors

0Ah

BYTE

media ID byte (see #01356)

0Bh

WORD

number of sectors per FAT

---DOS 2.13---

0Dh

WORD

number of sectors per track

0Fh

WORD

number of heads

11h

WORD

number of hidden sectors

---DOS 3.0+ ---

0Dh

WORD

number of sectors per track

0Fh

WORD

number of heads

11h

DWORD

number of hidden sectors

15h

11 BYTEs

reserved

---DOS 4.0+ ---

15h

DWORD

total number of sectors if word at 08h contains zero

19h

6 BYTEs

???

1Fh

WORD

number of cylinders

21h

BYTE

device type

22h

WORD

device attributes (removable or not, etc)

---DR DOS 5+ ---

15h

DWORD

total number of sectors if word at 08h contains zero

19h

6 BYTEs

reserved

---European MS-DOS 4.00---

15h

DWORD

total number of sectors if word at 08h contains zero (however, this DOS does not actually implement >32M partitions)

See Also:

#01395,#01664