BIOS parameter block
In computing, the BIOS parameter block, often shortened to BPB, is a data structure in the volume boot record (VBR) describing the physical layout of a data storage volume. On partitioned devices, such as hard disks, the BPB describes the volume partition, whereas, on unpartitioned devices, such as floppy disks, it describes the entire medium. A basic BPB can appear and be used on any partition, including floppy disks where its presence is often necessary; however, certain filesystems also make use of it in describing basic filesystem structures. Filesystems making use of a BIOS parameter block include  FAT12 (except for in DOS 1.x), FAT16, FAT32, HPFS, and NTFS. Due to different types of fields and the amount of data they contain, the length of the BPB is different for FAT16, FAT32, and NTFS boot sectors. (A detailed discussion of the various FAT BPB versions and their entries can be found in the FAT article.) Combined with the 11-byte data structure at the very start of volume boot records immediately preceding the BPB or EBPB, this is also called FDC descriptor or extended FDC descriptor in ECMA-107 or ISO/IEC 9293 (which describes FAT as for flexible /floppy and optical disk cartridges). FAT12 / FAT16. DOS 2.0 BPB. Format of standard DOS 2.0 BPB for FAT12 (13 bytes): DOS 3.0 BPB. Format of standard DOS 3.0 BPB for FAT12 and FAT16 (19 bytes), already supported by some versions of MS-DOS 2.11: DOS 3.2 BPB. Format of standard DOS 3.2 BPB for FAT12 and FAT16 (21 bytes): DOS 3.31 BPB. Format of standard DOS 3.31 BPB for FAT12, FAT16 and FAT16B (25 bytes): DOS 3.4 EBPB. Format of PC DOS 3.4 and OS/2 1.0-1.1 Extended BPB for FAT12, FAT16 and FAT16B (32 bytes): FAT12 / FAT16 / HPFS. DOS  4.0 EBPB. Format of DOS 4.0 and OS/2 1.2 Extended BPB for FAT12, FAT16, FAT16B and HPFS (51 bytes): FAT32. DOS 7.1 EBPB. Format of short DOS 7.1 Extended BIOS Parameter Block (60 bytes) for FAT32: Format of full DOS 7.1 Extended BIOS Parameter Block (79 bytes) for FAT32: NTFS. Format of Extended BPB for NTFS (73 bytes): exFAT BPB. exFAT does not use a BPB in the classic sense. Nevertheless, the volume boot record in sector 0 is organized similarly to BPBs.