A track is subdivided into sectors. To distinguish the sectors,they are sequentially addressed by natural numbers 0,1,2and so on.A sector is a primitive access unit.

• 磁道又分为扇区，为了区分这些扇区，用0、1、2等给扇区按顺序编上地址号，一个扇区是一个基本的存取单位。