Understanding GPT and UEFI

The IBM Personal Computer is equipped with a ROM BIOS and when mass storage media is present containing a master boot record (MBR) the end user will recognize this as their system hard drive containing their operating system and data. The MBR schema has in use successfully on IBM PC-compatible systems since 1983. Although this system is still widely in use there is a replacement being implemented that has caused much confusion among IT professionals.

• UEFI (Unified Extensible Firmware Interface) is a replacement for the old ROM BIOS on the personal computer.
• GPT (GUID Partition Table) is a replacement for the MBR partitioning schema on hard drives and mass storage media.

Don't you love it when an acronym contains within it another acronym? The G in GPT refers to GUID or Globally Unique IDentifiers.

Consider these things typically work in pairs. BIOS + MBR as the old system and UEFI + GPT as the modern replacement.

GPT disks contain five data structures:

• the protective MBR
• the main GPT header
• the main partition table
• the backup partition table
• the backup GPT header

See: Repairing GPT Disks by Rod Smith

See also:

• BIOS
• CMOS
• UEFI