a storage medium stores information on a plurality of tracks formed thereon , each of the tracks being divided into a plurality of sectors . the storage medium includes a physically formed sector beginning identifier provided at a leading portion of each sector , and an information storing portion . the information storing portion , another sector address portion at the trailing end of the information storing portion , includes at least one sector address portion at a leading end of the information storing portion , another sector address portion at the trailing end of the information storing portion , and a data portion provided between the two sector address portions .