In This article I am going to Continue my discussion of MBR which I started in Article: Understanding Master Boot Record (MBR)
An EBR, which consists of an extended partition table and the signature word for the sector, exists for each logical drive in the extended partition. It contains the information only on the first side of the first cylinder of each logical drive in the extended partition. The boot sector in a logical drive is usually located at either Relative Sector 32 or 63, depending on the drive translation. However, if there is no extended partition on a disk, there are no EBRs and no logical drives.
- The first entry in an extended partition table for the first logical drive points to its own boot sector.
- The second entry points to the EBR of the next logical drive.
If no further logical drives exist, the second entry is not used and is recorded as a series of zeroes.
If there are additional logical drives, the first entry of the extended partition table for the second logical drive points to its own boot sector.
The second entry of the extended partition table for the second logical drive points to the EBR of the next logical drive.
Note: The third and fourth entries of an extended partition table are never used.
The Relative Sectors field in an extended partition table entry shows the number of bytes that are offset from the beginning of the extended partition to the first sector in the logical drive.
The number in the Total Sectors field refers to the number of sectors that make up the logical drive.
The value of the Total Sectors field equals the number of sectors from the boot sector defined by the extended partition table entry to the end of the logical drive.
