说明：  设计五个算法,分别是先来先服务算法,最短寻道时间优先算法,扫描(SCAN)算法,循环扫描(CSCAN)算法,NStepSCAN算法.由人工输入当前的磁道数,由系统随即生成要访问的磁道
(The design of the five algorithms, namely, first-come first-serve algorithm, the shortest seek time priority algorithm, scanning (SCAN) algorithm, scanning cycle (CSCAN) algorithm, NStepSCAN algorithm. By manual input current tracks the number was generated by the system to access the track)