an Entity references as follows:
A master boot record (MBR) is a special type of boot sector at the very beginning of partitioned computer mass storage devices like fixed disks or removable drives intended for use with IBM PC-compatible systems and beyond. The concept of MBRs was publicly introduced in 1983 with PC DOS 2.0. MBRs are not present on non-partitioned media such as floppies, superfloppies or other storage devices configured to behave as such.