AbstractOne of the main goal of the operating system for the disk drives is to use the hardware efficiently. we can meet this goal using fast access time and large disk bandwidth that depends on the relative positions of the read-write head and the requested data. Since memory management allows multiprogramming so that operating system keeps several read/write request in the memory. In order to service these requests, hardware (disk drive and controller) must be used efficiently. To support this in disk drive, the hardware must be available to service the request. if the hardware is busy, we can’t service the request immediately and the new request will be placed in the queue of pending requests. Several disk scheduling algorithms are avail...