Example: "Microsoft's Fdisk utility can be used to create and update the master boot record."

An MBR, or "master boot record," is a special section on a hard disk that defines the disk partitions and contains the boot code. It is located in the first sector of the disk and is only 512 bytes in size.

Master boot records were introduced in the early 1980s and were used by DOS-compatible computers for over twenty years. However, MBRs can only define up to 2TB of space, which means they are not meant to be used by storage devices larger than two terabytes. Therefore, most computers now format disks using the GPT (GUID partition table), which does not have a two terabyte limit.

Updated: August 27, 2012