Consider the following Graph of disk scheduling and identify the disk…

This graph represents C-LOOK (Circular LOOK):

• Directional Service: The head moves in one direction (left to right in the graph, servicing requests like 11, 20, 28, 36, 45, 84, 125, 170, 172).

• No "End" Travel: Unlike SCAN or C-SCAN, the head does not go all the way to the disk end (0 or 199). It reverses immediately after servicing the last request in the current direction (at 172).

• Circular Return: After reaching the last request (172), it jumps back to the first request on the other side (11) without servicing any requests during the return trip. This "circular" jump is the defining feature of C-LOOK/C-SCAN.

• Differentiation:

  • SCAN/C-SCAN would touch the ends (0 or 199).

  • SSTF would zigzag based on the shortest distance, not move in a consistent sweep.

  • C-LOOK services in one direction, jumps back to the start of requests, and repeats, without hitting the physical disk boundaries unnecessarily.