Updating master boot code
) is one of the several parts of the master boot record.
It performs the first set of important functions in the process of booting.
This MBR code is usually referred to as a boot loader.
Approaches to slightly raise this limit assuming 33-bit arithmetics or 4096-byte sectors are not officially supported as they fatally break compatibility with existing boot loaders and most MBR-compliant operating systems and system tools, and can cause serious data corruption when used outside of narrowly controlled system environments.
A master boot code is used only on primary partitions.
Non-active partitions like those on an external drive that may store data like file backups, for example, don't need to be booted from because they don't contain an operating system and therefore have no reason for a master boot code.
Master boot code errors can happen due to anything from a virus attack that replaces the data with malicious codes, to physical damage to the hard drive.Specifically, in the typical generic master boot record, the master boot code consumes 446 bytes of the total 512-byte master boot record - the remaining space is used by the partition table (64 bytes) and the 2-byte disk signature.Assuming the master boot code is executed properly by BIOS, the master boot code hands off booting control to the volume boot code, part of the volume boot sector, on the partition on the hard drive that contains the operating system.Therefore, the MBR-based partitioning scheme is in the process of being superseded by the GUID Partition Table (GPT) scheme in new computers.A GPT can coexist with an MBR in order to provide some limited form of backward compatibility for older systems.