Master Boot Record

What Does Master Boot Record Mean?

The master boot record is a category of boot sector and the very first sector found in computer mass storage media such as fixed disks and removable computer drives. The master boot record provides the information on loading the operating system and also on the partition of the hard disk. The programs residing in master boot record help determine which partition needs to be used while booting. The master boot record is absent on non-partitioned devices such as super floppies, floppies or other devices configured in such a manner.


Techopedia Explains Master Boot Record

A master boot record has the following features: It is always located in the first sector of the hard disk. Cylinder 0, Head 0, Sector 1 is the specific address of the master boot record on the hard disk. It holds information about the organization of the partitions and the file system. A master boot record is generally 512 bytes or more. With help of the command FDISK or MBR, users can create a master boot record in Dos and Windows systems. The master boot record is capable of functioning as a chain boot loader independent of the operating system. The three main components of the master boot record are the master partition table, master boot code and disk signature. A corrupted master boot record can be repaired in Windows 7 and Windows Vista using the command "bootrec," available in system recovery options. In Windows XP, the command to be used for repairing is "fixmbr." One of the latest alternatives to to the master boot record is the GUID partition table. It’s a component of the unified extensible firmware interface specification.


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Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.