Master Boot Records and Partition Tables
1 Master Boot Record
The first 512 bytes of a computer disk is for the master boot record and partition table.
2 Master Boot Code
The first 446 bytes of the MBR contain the boot code—code like the first stage of GRUB boot loader that allows you to load an operating system.
3 Partition Table
The final 66 bytes contain a 64-byte partition table and a 2-byte signature.