Master Boot Record

aka:  MBR

A small program that is executed when a computer is booting up, which identifies how and where an Operating System (OS) is located so that it can be booted into the computer’s main storage or Random Access Memory (RAM).  Typically the MBR resides on the first sector of the hard drive.

The MBR is also sometime called the Partition Sector because it includes a table that locates each partition that the hard disk has been formatted into.

The MBR also contains a program that reads the boot sector record of the partition containing the Operating System to be booted into RAM.  That record contains a program that loads the rest of the Operating System into RAM.