标题柱面、磁头及扇区——Cylinders,Heads and Sectors

　　Cylinders are concentric regions on the hard disk platters with cylinder 0 usually located at the outer edgeCylinder numbers start at zero so if your hard disk has 900 cylinders，valid cylinder numbers are from 0-899.
　　柱面是指硬盘盘片上具有相同半径的区域，其0柱面通常位于硬盘外缘。柱面号以0开始，因此，如果硬盘有900个柱面，则有效的柱面号为0~899。
　　The heads of a hard disk are used to read and write data.Heads are mounted on an actuator that positions them to a given cylinder locationn.Head numbers start at zero so if your drive has 9 heads，valid head numbers are from 0-8.
　　硬盘的磁头用于读写数据。磁头安装在一个使它们定位于给定柱面的驱动臂上。磁头号以0开始，因此，若硬盘有9个磁头，有效的磁头号为0~8。
　　A sector is the smallest physically addressable unit of storage on a hard disk. Most hard disks have 512 bytes per sector.Sector numbers start at one so if your drive has 17 sectors，valid sector numbers are from 1-17.
　　扇区是硬盘上可编址的最小物理存储单元。大多数硬盘的每扇区为512字节。扇区号从1开始，这样，如果硬盘有17个扇区，则有效的扇区号为1~17。