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Vilma Software Hal - Master Boot Record

Master Boot Record

The Master Boot Record is located at the physical beginning of a hard disk. It includes the fallowing elements

  • master bootstrap loader code (446 bytes)  - a small program witch are executed at the startup to boot the operating system.

  • subsequent, identically structured partition records.

  • validation pattern - to guard against booting an MBR when it has never been set up, the BIOS checks for a special pattern (55AA) in the last word of the MBR (immediately following the partition table). Any valid MBR contain this pattern.

status indicator - This is used to indicate the status of a partition (i.e. whether or not it is the active partition). There are only two legal values; 0x80 flags an active partition, and 0x00 flags all other partitions. Any other value may cause the partition table to be treated as corrupt.

head number
- Head numbers run from 0 to n-1, where n is the total number of heads on the drive. The starting head number is the first head used by the partition, and the ending head number is the last head used by the partition.

partition sector - The first or last sector of the partition is called "start sector" / "last sector".

Operating System Indicators
0x00 Empty partition-table entry
0x01 DOS FAT12
0x02 XENIX  /root file system
0x03 XENIX  /usr file system
0x04 DOS FAT16 (up to 32 MB)
0x05 DOS 3.3+ extended partition
0x06 DOS 3.31+ FAT16 (over 32 MB)
0x07 OS/2 HPFS, Windows NT NTFS, Advanced Unix
0x08 OS/2 v1.0-1.3, AIX bootable partition, SplitDrive
0x09 AIX data partition
0x0A OS/2 Boot Manager
0x0B Windows 95+ FAT32
0x0C Windows 95+ FAT32 (using LBA-mode INT 13 extensions)
0x0E DOS FAT16 (over 32 MB, using INT 13 extensions)
0x0F Extended partition (using INT 13 extensions)
0x11 Hidden FAT-12
0x12 COMPAQ configuration partition
0x14 Hidden FAT-16 (up to 32MB)
0x16 Hidden FAT-16, 'BigDOS' (over 32MB)
0x17 Hidden NTFS partition
0x18 AST Windows swapfile
0x1B Hidden Windows 95 FAT32 partition
0x1C Hidden Windows 95 FAT32 partition (using LBA-mode INT 13 extensions)
0x1E Hidden LBA VFAT partition
0x24 NEC DOS 3.x
0x35 OS/2 JFS
0x38 THEOS ver.3 2gb partition
0x39 Plan 9; THEOS V4 spanned partition
0x3A THEOS V4 4gb partition
0x3B THEOS V4 extended partition
0x3C PartitionMagic recovery partition
0x3D Hidden Novell Netware
0x40 Venix 286
0x41 Linux/Minix (sharing disk with DRDOS); Power PC Reference platform boot; Personal RISC boot
0x42 LINUX swap (sharing disk with DRDOS); Secure File System
0x43 LINUX native (sharing disk with DRDOS)
0x45 Boot-US Boot Manager; Priam
0x4C Oberon
0x4D QNX 4.2 Primary
0x4E QNX 4.2 Secondary
0x4F QNX 4.2 Tertiary; Oberon
0x50 OnTrack Disk Manager; Lynx RTOS; Oberon, read-only partition
0x51 OnTrack Disk Manager; Novell Netware
0x52 CP/M; Microport SysV/AT
0x53 Disk Manager 6.0
0x54 Disk Manager 6.0 Dynamic Drive Overlay
0x55 EZ-Drive
0x56 Golden Bow VFeature
0x57 DrivePro
0x5C Priam EDisk
0x61 SpeedStor
0x63 UNIX System V (SCO, ISC Unix, UnixWare, ...); Mach; GNU Hurd
0x64 PC-ARMOUR; Novell Netware 2.xx
0x65 Novell Netware 3.xx or 4.xx
0x66 Novell Netware
0x67 Novell Netware
0x68 Novell Netware
0x69 Novell Netware
0x70 DiskSecure Multi-Boot
0x74 Scramdisk
0x75 PC/IX
0x78 XOSL multiboot loader
0x80 Minix 1.1 ... 1.4a
0x81 Linux partition
0x82 Linux Swap partition, Solaris (Unix)
0x83 Linux native file system (ext2fs/xiafs)
0x84 OS/2 hidden partition; hibernation partition
0x85 Linux EXT
0x86 FAT16 volume/stripe set (Windows NT)
0x87 HPFS fault-tolerant mirrored partition, NTFS volume/stripe set
0x8B NT FAT-32 (up to 2048GB) volume set
0x8C NT FAT-32 (up to 2048GB) LBA volume set
0x8E Linux Logical Volume Manager partition
0x93 Amoeba file system; hidden Linux file system
0x94 Amoeba bad block table
0xA0 Hibernation partition
0xA1 Hibernation partition
0xA5 BSD/386; FreeBSD/NetBSD/386BSD
0xA6 OpenBSD
0xA7 NextStep
0xA9 NetBSD
0xAA Olivetti FAT-12 service partition
0xB7 BSDI BSD/386 file system
0xB8 BSDI BSD/386 swap
0xBE Solaris boot partition
0xC0 DR-DOS/Novell DOS secured partition
0xC1 DRDOS/secured (FAT-12)
0xC6 Corrupted FAT16 volume/stripe set (Windows NT)
0xC7 Corrupted NTFS volume/stripe set
0xD8 CP/M-86
0xDB CP/M; Concurrent CP/M; Concurrent DOS; CTOS
0xDF BootIt
0xE1 SpeedStor FAT-12 extended
0xE3 SpeedStor
0xE4 SpeedStor FAT-16 extended
0xF1 SpeedStor
0xF2 DOS 3.3+ secondary partition
0xF4 SpeedStor large partition
0xFB VMWare file system
0xFC VMWare swap
0xFD Linux RAID
0xFE PS/2 IML partition; SpeedStor; LANstep
0xFF BBT (Bad Blocks Table)


partition track - The first cylinder of the partition.

relative sectors - This is an alternative way of describing the location of the partition. The relative starting sector is the offset of the start of the partition, in sectors, from the MBR itself (i.e. from the start of the whole disk).

partition length - The size is simply the number of sectors which make up the actual partition.



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