A boot flag is a 1-byte value in a non-extended partition record, within a master boot record. It appears at the beginning of a partition record, as the value 0x80. A value of 0x00 indicates the partition does not have the boot flag set. Any other value is invalid.
Its primary function is to indicate to a MS-DOS/MS Windows-type boot loader which partition to boot. In some cases it is used by Windows XP/2000 to assign the active partition the letter "C:". The active partition is the partition where the boot flag is set. DOS and Windows allow only one boot partition to be set with the boot flag.
- "http://www.diydatarecovery.nl/kb_mbr_article.htm". DIY DataRecovery. Retrieved 2014-12-14.
- Goodell, Dan. "Fixing Windows 2000/XP Drive Letters". Understanding MultiBooting and Booting Windows from an Extended Partition. Retrieved 2014-12-14.
- "Parted User's Manual - 4. Boot Loaders". GNU Project. Retrieved 2014-12-14.
- "Mark a partition as active". Microsoft. Retrieved 2014-12-14.