Editing BIOS parameter block (section)

{{Short description|Data structure in the volume boot record}}
{{Use dmy dates|date=April 2019|cs1-dates=y}}
{{Use list-defined references|date=January 2022}}
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 [[Computer data storage|data storage]] [[Volume (computing)|volume]]. On partitioned devices, such as [[hard disk drive|hard disks]], the BPB describes the volume partition, whereas, on unpartitioned devices, such as [[floppy disk]]s, 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]], [[High Performance File System|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.<ref name="Microsoft"/> (A detailed discussion of the various FAT BPB versions and their entries can be found in the [[FAT BPB|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).