MORE INFORMATION
A hard disk's master boot record (MBR) is located in the first sector of
the disk (cylinder 0, side 0, sector 1). The partition table is located at
offset 01BE, containing up to four 16-byte entries. The fourth byte of
each partition table entry is used to mark the partition type.
MS-DOS began supporting hard disks in version 2.0.
MS-DOS Versions 2.x
MS-DOS 2.x supports one type 01 partition of up to 15 megabytes (MB) in
size, which uses a 12-bit file allocation table (FAT). Fdisk creates only
one MS-DOS partition per drive.
MS-DOS 3.0
MS-DOS 3.0 supports partitions larger than 15 MB using a 16-bit FAT, which
allows a smaller cluster size and more efficient disk usage. As a result,
MS-DOS 2.x hard disks larger than 15 MB are incompatible with later
versions of MS-DOS. Fdisk creates only one MS-DOS partition per drive.
MS-DOS 3.3
MS-DOS 3.3 introduces support for more than one logical drive per hard
disk. Logical drives are treated as completely separate disks under
MS-DOS, even though they may occupy the same physical hard disk.
This is supported by using nonbootable MS-DOS partitions known as extended
MS-DOS partitions. Fdisk reports these as EXT DOS; other MS-DOS partitions
are reported as PRI DOS (for primary MS-DOS). Each primary MS-DOS
partition is a logical drive, and extended MS-DOS partitions contain from
1 to 23 logical drives (MS-DOS supports drive letters up to Z). Logical
drives in extended MS-DOS partitions have the same FAT type as a primary
MS-DOS partition of the same size.
Only one PRI DOS partition and one EXT DOS partition is allowed per drive.
On computers with two physical hard disks, a PRI DOS partition is not
required on the second physical disk. A PRI DOS partition is required on
the first physical disk. (MS-DOS does not support more than two physical
disks.)
MS-DOS 4.0
MS-DOS versions 4.0 and later support logical drives larger than 32 MB.
Full usage of these logical drives requires the MS-DOS program Share.exe
to be loaded in MS-DOS 4.0.
The following table explains the versions 4.x and later MS-DOS partition
types:
Partition Fdisk Starting in
Type Reports Size FAT Type MS-DOS version
------------------------------------------------------------------
01 PRI DOS 0-15 MB 12-Bit 2.0 (a)
04 PRI DOS 16-32 MB 16-Bit 3.0
05 EXT DOS 0-2 GB (b) n/a 3.3
06 PRI DOS 32 MB-2 GB (b) 16-bit 4.0
(a) 15-MB size limitation extended in version 3.0.
(b) 2 GB (gigabytes) includes a limit of 1024 cylinders per drive
imposed by the standard AT ROM BIOS interrupt 13 protocol.
MS-DOS 5.0
MS-DOS versions 5.0 and later support up to eight physical hard disks.
Share.exe is not required for full large-drive support; this support is
included in the MS-DOS kernel.
MS-DOS versions 5.0 and later support the same partitioning strategy as
version 4.x, including Fdisk's inability to create more than one primary
MS- DOS partition on a physical disk. However, because some original
equipment manufacturer (OEM) partitioning software allows you to create
more than one primary MS-DOS partition, MS-DOS versions 5.0 and later have
kernel support for up to four primary MS-DOS partitions. This makes it
easier to upgrade from previous versions of OEM-modified MS-DOS. Fdisk
still creates only one PRI DOS partition on a physical disk.
NOTE: Many OEMs have changed their versions of MS-DOS to support more than
one primary MS-DOS partition, larger type 04 partitions, and new partition
types.
Windows 95
Windows 95 supports two new partition types (0E and 0F) to support the
logical block addressing (LBA) INT13h extensions as specified in the
Windows 95 Driver Development Kit (DDK).
Partition Fdisk Starting in
Type Reports Size FAT Type version
------------------------------------------------------------------
01 PRI DOS 0-15 MB 12-Bit MS-DOS 2.0
04 PRI DOS 16-32 MB 16-Bit MS-DOS 3.0
05 EXT DOS 0-2 GB n/a MS-DOS 3.3
06 PRI DOS 32 MB-2 GB 16-bit MS-DOS 4.0
0E PRI DOS 32 MB-2 GB 16-bit Windows 95
OF EXT DOS 0-2 GB n/a Windows 95
Types 0E and 0F require extended Int13 support.
NOTE: Type 0E is the same partition type as 06, and 0F is the same as 05.
However, applications should use the (LBA) INT13h extension's read/write
functions to read from or write to the drive instead of the normal
Cylinder/Head/SectorPerTrack (CHS) INT13h functions because the hard disk
has more than 1024 cylinders and/or more than 16,711,680 sectors. Note
that earlier versions of FDISK recognize these Windows 95 partitions as
NON-DOS partitions.
Windows 95 OEM Service Release 2 and Windows 98
Windows 95 OEM Service Release 2 (OSR2) and Windows 98 support two new
partition types (0B and 0C) to support the FAT32 file system. For
additional information about FAT32, please see the following article in
the Microsoft Knowledge Base:
ARTICLE ID: 154997
TITLE : Description of the FAT32 File System
The partition types supported by OSR2 and Windows 98 are as follows:
Partition Fdisk Starting in
Type Reports Size FAT Type version
---------------------------------------------------------------------
01 PRI DOS 0-15 MB 12-Bit MS-DOS 2.0
04 PRI DOS 16-32 MB 16-Bit MS-DOS 3.0
05 EXT DOS 0-2 GB n/a MS-DOS 3.3
06 PRI DOS 32 MB-2 GB 16-bit MS-DOS 4.0
0E PRI DOS 32 MB-2 GB 16-bit Windows 95
0F EXT DOS 0-2 GB n/a Windows 95
0B PRI DOS 512 MB - 2 terabytes 32-bit OSR2
0C EXT DOS 512 MB - 2 terabytes 32-bit OSR2
Types 0E, 0F, and 0C require extended Int13 support.