Solution

The correct answer is C-LOOK.

Key Points

• C-LOOK (Circular LOOK) is a disk scheduling algorithm that is an optimized version of the LOOK algorithm.
• In C-LOOK, the disk arm only goes as far as the last request in each direction, then immediately reverses direction without going to the end of the disk.
• This minimizes the movement of the disk arm and reduces the total seek time.
• When the disk arm reaches the end of the queue in one direction, it jumps to the other end of the queue and starts servicing requests in the opposite direction.
• This is different from the C-SCAN algorithm, where the disk arm goes to the end of the disk and then starts from the beginning.

Additional Information

• The queue given is: 84, 125, 11, 36, 170, 20, 172, 45.
• Assume the initial position of the disk arm is at 50.
• Using the C-LOOK algorithm, the disk arm will first service requests in one direction until it reaches the last request, then it will jump to the other end of the queue and continue servicing requests.
• Here’s how the sequence looks like: 84, 125, 170, 172, then jump back to the start and service: 11, 20, 36, 45.
• This minimizes the seek time compared to other algorithms like SCAN or C-SCAN.