Suppose in the First Come First Served Disk Scheduling Algorithm the order of request is (90, 150, 50, 140, 30, 20) and the current position of read/write head is 40, then the total distance covered by the disk ann would be

The correct answer is Option 3) 520.

Key Points

• First Come First Served (FCFS) Disk Scheduling Algorithm serves the requests in the order they arrive.
• Given:
  • Initial head position = 40
  • Request queue = (90, 150, 50, 140, 30, 20)
• We calculate the total distance moved by the disk head step-by-step:

Additional Information

• FCFS Characteristics:
  • Simple to implement
  • Processes requests in the order of arrival
  • Does not optimize seek time
• Other disk scheduling algorithms:
  • SSTF (Shortest Seek Time First): Chooses the request closest to current head position
  • SCAN: Moves head in one direction, servicing requests in order until end is reached, then reverses
  • LOOK: Like SCAN, but stops at last request instead of going to the end of disk