Circular Scan (C-Scan) is a disk scheduling algorithm that is similar to the Scan (Elevator) algorithm. In C-Scan, the disk head moves from the start to the end of the disk, services all requests that are in that direction, and then immediately moves to the other end of the disk without servicing any requests.
C-Scan is a variation of the Scan algorithm, but it has a few differences. Unlike Scan, in C-Scan the disk head does not service requests in the reverse direction when it reaches the end of the disk. Instead, it immediately moves to the other end of the disk and continues servicing requests in the same direction.
The process of scheduling disk requests in C-Scan is as follows:
Keep track of the current position of the disk head: The current position of the disk head can be stored in a simple variable.
Keep track of the list of disk requests: The disk requests can be stored in an array or a linked list. Each entry should include the cylinder number of the disk request.
Service disk requests: A loop can be used to iterate over the list of disk requests and select the next disk request to be serviced. The disk head moves from the start to the end of the disk, services all requests in that direction, and then moves immediately to the other end of the disk without servicing any requests.
Update the current position of the disk head and the list of disk requests: After a disk request has been serviced, the current position of the disk head should be updated to the cylinder number of the disk request that was just serviced, and the disk request should be removed from the list of disk requests.
The total seek time for all disk requests can be calculated and compared to other disk scheduling algorithms to determine the best approach for a given set of disk requests.
C-Scan has several advantages over other disk scheduling algorithms. For example, it is a fair and predictable algorithm, as disk requests are serviced based on the order in which they are encountered. Additionally, it is more efficient than the FCFS disk scheduling algorithm, as it reduces the total seek time by moving the disk head in one direction and servicing disk requests along the way.
However, C-Scan also has some disadvantages. For example, it may not be well-suited for systems with a large number of disk requests, as the time required to seek the disk can become quite large. Additionally, it may not be the best choice for systems with heavy disk I/O, as it may not be able to keep up with the high number of disk requests.
In conclusion, the Circular Scan (C-Scan) disk scheduling algorithm is a variation of the Scan algorithm that is designed to reduce the total seek time by moving the disk head in one direction and servicing disk requests along the way. While it provides a fair and predictable approach to disk scheduling, it may not be the best choice for systems with a large number of disk requests or heavy disk I/O. When choosing a disk scheduling algorithm, it's important to consider the specific needs and requirements of your system, as well as the characteristics of your workload, to determine the best approach for your specific situation.
