  OBR (OS Boot Record) that is the operating system boot sector, usually located in the hard disk 0 track a cylinder one sector (this is for DOS, and for those with multi-boot system is activated in the corresponding primary partition / The first one extended partition sector), is the first sector which the operating system can directly access, it also includes a boot program and a BPB (BIOS Parameter Block) record parameters of this partition table. In fact, every logical partition has an OBR, its parameters depending on the size of the partition; the type of operating system is different.
The main task of the guiding-process is to determine whether the two documents before the operating system boot files on the root directory of the district (for example, MSDOS, or originated in the MSDOS of Win9x/Me the IO.SYS and MSDOS.SYS). If so, put the first file is read into memory, and given control to the file. BPB parameter block record the start partition sector, end sector, file storage format, hard disk media descriptor, the size of the root directory, FAT number, the size of  distribution unit (Allocation Unit, previously known as cluster) important parameter. OBR generated by the high-level formatting program (such as DOS-Format.com)
