What is MBR | Understanding the Master Boot Record

What is Master Boot Record(MBR)?

MBR stands for master boot record. The data located in the first sector of a hard drive or removable drive is known as the master boot record(MBR) In order for the computer's main storage or random access memory to be booted called as loaded, it must know how and where the system operating system(OS) is located(RAM). A program that read the boot sector record of the partition containing the OS booted is also included in the MBR. The programme that loads the remainder of the OS into RAM is then contained in that record. 

As compared to On a GPT(GUID partition table), Windows can have up to 128 partitions without building extended partitions and support drive larger than one million terabytes. On the other hand, An MBR only supports the four standard or primary partitions and also does not support drives larger than 2 TB. An MBR must expand the partitions in order to support additional logical partitions. You can check out more differences related to this two drives, and learn more about MBR vs GPT in this article.

There are three main parts of the Master boot record

Master boot routine

The variable load coder, which the MBR needs, is part of the 446-byte master boot routine. The MBR transfers control to the operating system listed in the partition table once the hard drive has been booted.

Table of Disk partitions(DPT)

Storage device partitions are described in the partition table. In each hard drive, the first sector(cylinder 0, head 0, and sector 1, MBR) is where the disk partition table is found. Each partition entry is 16 bytes long, giving the partition table a total length of 64 bytes. Therefore, an MBR disk can have a maximum of 4 partitions. Users can create extended partitions which can be divided into multiple logical drives if they require more partitions.

Code of identification

The MBR can be recognised by its identification code. It has a value of AA55H or 55AAH in 2 bytes.

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