Chapter 11, Problem 56E

Program Plan Intro

Disk scheduling:

• In a computer, multiple processes run over the same time.
• To handle this multiple processes, the operating system decides which process has to be executed first. This technique is called as disk scheduling.
• There are different types of scheduling algorithms. They are as follows:
  • First-come, First-served (FCFS)
  • Shortest-Seek-Time-First (SSTF)
  • SCAN

SCAN disk scheduling algorithm:

• The SCAN algorithm is called as elevator algorithm.
• In the SCAN algorithm, the disk arm starts at one end of the disk and moves toward the other end.
• It processes the request for each cylinder until it gets to the other end of the disk.
• At the other end, it reverses the direction of head movement.
• The head continuously moves back and forth across the disk based upon the closest distance.