Boot sector

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A boot sector is usually the first sector of a bootable medium . It contains information or a program that is necessary to start an operating system , or it is the operating system itself. Further subsequent sectors (data blocks) can also be involved.

Use of the term

The term boot sector ( English boot sector or bootsector ) mostly describes a start program that was used on the most common computer architectures at the beginning of the era of personal computers to start the actual operating system. A small program is executed that is supposed to start the kernel . However, due to the rapid development in the area of ​​operating systems, this principle quickly reached its limits. While IBM PCs expanded the concept with complex chain loaders to integrate new functions, the firmware of Macintosh computers from Apple was further developed so that it reads the relevant information for starting the operating system from the boot sector and loads the drivers or the kernel directly.

On almost all external storage media that are PC or Windows compatible, there is a “ Master Boot Record ” (MBR) in the boot sector. The partition table contained therein is supported by all common operating systems, which enables access to the individual partitions. Strictly speaking, z. B. car radios or MP3 players , the audio files from z. B. play a USB stick , can handle such a boot sector, but these devices only use the included partition table, but not the included start program ( English boot code ).

Since the replacement of the BIOS by UEFI boot sector is the also in IA-32 - architecture not directly used to start the operating system, although for compatibility still a partition table included launcher (MBR, see also " protective MBR " ), but which are no longer used.

Common boat sectors

IBM PC Compatible Computer (x86):

  • Master Boot Record , the first sector on the hard disk or other partitioned data media
  • Volume boot record , also called partition boot record, from the first sector on the partition ( the only boot sector for non-partitioned data media such as floppy disks )

Apple Macintosh (m68k and PowerPC):

Amiga (m68k and PowerPC):


Individual evidence

  1. ^ Rob Braun: System 6 Boot Process . In: Mac68k Wiki. December 10, 2012, accessed February 24, 2013 .