Master Boot Record

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A master boot record (MBR) is a special type of boot sector at the very beginning of partitioned compute R mass storage devices like fixed disks or removable drives intended for use with IBM pc-compatible systems and beyond. The concept of MBRs is publicly introduced in 1983 with PC DOS 2.0.

The MBR holds the information on how the logical partitions, containing file systems, is organized on that medium. The MBR also contains executable code to function as a loader for the installed operating system-usually by passing Contro L over to the loader's second stage, or in conjunction with each partition ' s volume Boot Record (VBR). This MBR code was usually referred to as a boot loader. ^[1]

A master boot record (master boot record, abbreviation: MBR), also known as the Primary boot sector , is the first sector that must be read when the computer accesses the hard disk, and its three-dimensional address on the hard disk is (cylinder, head, sector) = (0 , 0, 1). When delving into the internal structure of the main boot sector, it is sometimes referred to as the "Master Boot Record" (MBR), followed by 4 16-byte "Disk partition Table" (DPT), and a 2-byte end flag (55AA) for the initial 446-byte content. Therefore, when using the term "Master boot Record" (MBR), it is necessary to determine whether it refers to the entire primary boot sector or the first 446 bytes of the primary boot sector, depending on the situation.

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Standard MBR structure

Address			Description		Length (bytes)
Hex	Oct	Dec
0000	0000	0	Code Area		(max. 446)
01B8	0670	440	Select Disk Flag		4
01BC	0674	444	generally null value; 0x0000		2
01BE	0676	446	Standard MBR partitioned table planning (four primary partition table entries in bytes)		64
01FE	0776	510	35.	MBR valid flag: 0X55AA	2
01FF	0777	511	AAh
MBR, Total size: 446 + 2 =

The main boot sector records information about the hard disk itself and the size and location of each partition of the hard disk, which is an important entry point for data information. If it is compromised, the basic data structure information on the hard disk will be lost, and it will be necessary to re-access the original data after a tedious and tentative reconstruction of the structure information. The information in the main boot sector can be written through any partition tool software based on an operating system, but there is no specific relationship with an operating system, that is, any operating system can be booted as long as a valid master boot record is created (the operating system is created on top of the advanced formatted hard disk partition, is associated with a certain file system).

Master Boot Record