Patent ID: 7474485

Claim:
A magnetic disk medium having tracks formed thereon, each track being divided into a plurality of sectors to which servo data is written, wherein each track is also divided into a plurality of blocks each including one or more of said plurality of sectors, said one or more sectors being sequentially arranged along said each track; wherein each block stores a positional information bit string which includes address information corresponding to a position of said each block on the track; wherein said positional information bit string is made up of a position code and an identification code, said position code including said address information, said identification code being used to identify the start or the end of said position code; wherein said positional information bit string is divided into a plurality of portions each stored in a different sector of the block, said each portion forming a predetermined part of servo data stored in said different sector; wherein said identification code includes a string of M bits each having a first bit value and further includes a bit having a second bit value which immediately precedes or succeeds said string (where M denotes an integer equal to or larger than 2); wherein said position code includes a plurality of strings each having a length less than M bits and further includes bits each having said second bit value, said plurality of strings being separated from one another by one of said bits having said second bit value, said plurality of strings collectively forming an address bit string corresponding to said address information; wherein said address bit string is a binary block number for sequentially numbering each block on a track; and wherein when the proportion of said address bit string in said positional information bit string stored in each block is maximized, the number of blocks on each track is set based on the largest block number that can be expressed by said address bit string.