Partitions use CHS (cylinder/head/sector) numbering.

The partition table is located on CHS 0,0,1.

Head: 1 8 bits

Sector: 6 bits

Cylinder: 10 bits

Each partition in the table has a starting position and an ending position. They had better not overlap!

0      1       Boot label. Tell computer to boot from this partition
1      1       Starting head
2      1       Lower 6 bits (bit 0 to bit 5) is starting sector.
               Higher 2 bits (bit 6 to bit 7) is the higher bits of starting cylinder
3      1       The lower 8 bits of starting cylinder
4      1       Partition type
5      1       Ending head
6      1       Lower 6 bits (bit 0 to bit 5) is ending sector.
               Higher 2 bits (bit 6 to bit 7) is the higher bits of ending cylinder
7      1       The lower 8 bits of ending cylinder
8      4       Leading sectors of this partition
12     4       Number of sectors of this partition

(this data is old, isn't it? how do we handle high capacity drives?)