The Master Boot Record (MBR) is the first sector on a hard drive that comprises special data about the operating system that was utilized to start the computer. “Sector zero,” “master boot block,” or “master partition boot sector” are other terms for the Master Boot Sector. In this article, you will understand what MBR is, the parts of MBR(Master boot record), the Features of MBR, and more!

 

 

What is MBR (Master Boot Record)?

The Master Boot Record (MBR) is located in the first sector of the hard disk and contains the partition table, which serves a specific purpose. When you start the computer by pressing the power button, the BIOS checks the boot loader stored in the MBR, which is in the first sector of the hard disk. The bootloader then loads the operating system into the main memory. This process is known as Booting. The partition table outlines how the hard disk is divided structurally, including details like the file system used, the start and end sectors of each partition, and the size of each partition.

To determine the disc from various discs, the operating system makes use of the disc signature. For the reason that the disc holds the data that the computer’s BIOS (Basic Input/Output System) needs to find the operating system and begin the boot procedure, the MBR is required to start the computer. The GUID Partition Table (GPT) is the new partitioning technique that is used for higher disc capacities because MBR can only manage disc sizes up to 2 TB. But GPT is used for disks larger than two terabytes (TB).

 

 

Parts of MBR(Master boot record)

• Master boot routine: The 446-byte master boot routine involves a variable load coder, which is important data for the MBR. The MBR transfers power to the operating system set down in the partition table immediately as the hard drive boots up. 
• Disk partition table (DPT): The DPT, which is located in the first sector of the hard disk, has details on the partitions’ positions. It comprises 64 bytes. Extended partitions can be created as required, with a maximum of four partitions (16 bytes each).
• Identification code: The MBR can be determined by its identification code. It has a value of 55AAH or AA55H and its size is 2  bytes.

 

Features of MBR

• Boot Loading Ability: Boot loader code is present in the MBR. The boot loader which aids in loading the operating systems into the main memory known as the booting process.
• Easy To Use: It can be used effortlessly, and users can easily control and maintain their disc partitions with MBR. 
• Disk Determination: MBR makes use of a disc signature to recognize the disc. 
• Versatility: Many operating systems like Windows, Linux, and macOS, as well as many different devices, use the Master Boot Record (MBR).

 

 

Differences between the Master Boot Record and GUID Partition Table

Feature	MBR	GPT
Boot Code and Data Preservation	Preserves boot code only.	Preserves boot code and all partition-related data.
Maximum Number of Partitions	Supports up to 4 primary partitions.	Supports up to 128 partitions.
Maximum Disk Size	Supports up to 2TB disk size.	Supports up to 9.44 million TB disk size.
Data Recovery	No guaranteed data recovery.	Data is stored throughout the drive for guaranteed recovery.
Error Checking	No built-in error checking.	Uses CRC for error detection.
Compatibility	Compatible with older systems and Windows OS.	Requires UEFI for full support; faster boot with SSDs.

 

Limitations of Master Boot Record (MBR)

• Disk Capacity: MBR can only be supported with discs up to 2 TB in size, it cannot be supported for discs of sizes greater than that. For that, GPT could be utilized. 
• Constraints imposed by older BIOS systems: MBR cannot be used with the latest UEFI (Unified Extensible Firmware Interface) systems because it is only compatible with older BIOS (Basic Input/Output System) systems.
• Absence of redundancy: The MBR does not have any integrated redundancy process, so damage to the MBR could hinder a system from getting started. 
• Limited Partitions: The MBR can have a maximum of up to four partitions, or three main partitions and one extended partition.

 

 

How do we fix issues with the Master Boot Record (MBR)?

Windows cannot start (no system boot) because of a flawed master boot record, so the “fixing” process has to be completed outside of Windows. Here are some recommended commands to support getting Windows to boot again. The problem is that implementing these methods is a thoughtful and fragile process. As a consequence, beginners might not be able to finish them precisely. 

Moreover, each version of Windows has special commands and rules. Let’s look at commands for each version of Windows (7, 8, 10, Vista, XP). 

Window Version	Command
Window XP	Fixmbr Command
Window Vista	Bootrec Command
Window 7	Bootrec Command
Windows 10 and 8	Bootrec Command

 

Conclusion

The Master Boot Record (MBR) is an essential part of a computer’s startup process, situated at the beginning of the hard disk. It controls how the hard drive is divided and helps in loading the operating system. MBR has limitations, like supporting up to 2TB disks and having no integrated data recovery. Despite this, it remains widely used for its simplicity and compatibility with different operating systems. 

 

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