The master boot record (MBR) is code written on the first sector of a HDD. It keeps information that permits the OS to boot. It is used by Microsoft Windows OS.

• Significance
When a system starts, the processor is told to execute the code placed on the first part of the HDD. Manufacturers have made this the default location so that there is no puzzlement in programming.

• Function
The MBR uses bootstrapping in order to start the OS. This activates and tests hardware like keyboards and mice.

• Considerations
The MBR's size is restricted to two terabytes. Because of this, options are being developed, like GUID in Linux.

• Recovery
If the MBR is by chance deleted, Windows can restore it in Recovery Mode by using the FixMbr code.

• Warning
Because of its significance, the MBR is the main target for advanced computer viruses.