The BIOS Parameter Block (BPB) is part of the Boot Record on computer drives. The BPB identifies the disk parameters, such as bytes per sector, sectors per track and tracks per disk. It also identifies special sectors or tracks that are set aside for other purposes, such as engineering sectors.

The BPB allows the operating system to understand the format of the disk. If the BPB is damaged or missing, the disk is unusable until a new Boot Record is recorded on Sector 0,0,1.