[2] EBRs have essentially the same structure as the MBR; except only the first two entries of the partition table are supposed to be used, besides having the mandatory boot record signature (or magic number) of 0xAA55 at the end of the sector.
[1] This 2-byte signature appears in a disk editor as 0x55 first and 0xAA last, because IBM-compatible PCs store hexadecimal words in little-endian order (see table below).
The IBM Boot Manager (included with OS/2 operating systems and some early versions of Partition Magic), adds at least one 9-byte entry (starting at offset 0x18A) to each EBR sector.
[4] DR DOS 6.0 and higher support secured extended partitions using 0xC5, which are invisible to other operating systems.
Since non-LBA-enabled versions of DR-DOS up to including 7.03 do not recognize the 0x0F partition type and other operating systems do not recognize the 0xC5 type, this can also be utilized to occupy space up to the first 8 GB of the disk for use under DR-DOS (for logical drives in secured or non-secured partitions), and still use 0x0F to allocate the remainder of the disk for LBA-enabled operating systems in a non-conflictive fashion.
[6] The following are general rules that apply only to values found in the 4-byte fields of an EBR's partition table entries (cf.
Remarks: The diagrams above are not to scale: The thin white lines between each "EBR" and its logical "partition" represent the remainder of an unused area usually 63 sectors[note 2] in length; including the single EBR sector (shown at a greatly exaggerated size).
Remark: Neither a tiny extended partition with only 3 MB nor a hard drive with 20 sectors per track are realistic but these values have been chosen to make this example more readable.
Details for the FAT and NTFS partitions stripped, the line annotated with Linux is /dev/hda6 with an extended file system.