Question

Consider a disk queue holding requests to the following cylinders in the listed order: 116,22,3,11,75,185,100,87, sing the C-SCAN scheduling algorithm. what is the order that the requests are serviced, assuming the disk head is at cylinder 88 and mowing upward through the cylinders?

a. 100−116−185−3−11−22−75−87
b. 116−22−3−11−75−185−100−87
c. 100−116−185−87−75−22−11−3
d. 87−75−100−116−185−22⋅11−3

Answer 1

The order of servicing using the C-SCAN scheduling algorithm, starting at cylinder 88 and moving upward, is 100, 116, 185, then wrapping around to 3, 11, 22, 75, and finally 87.

Step-by-step explanation:

The C-SCAN (Circular SCAN) scheduling algorithm services all the requests in one direction until it reaches the end of the disk and then jumps directly to the other end and resumes servicing requests from there. With the disk head starting at cylinder 88 and moving upward, the servicing order is determined first by attending to requests higher than 88, then wrapping around to the lowest request and moving upwards again.

Starting from cylinder 88 and moving upward, the disk head moves to cylinders: 100, 116, then 185. Since 185 is the highest in our list, the disk head would then jump to the lowest cylinder, 3, and move up servicing 11, 22, 75, and lastly 87, before reaching 88 again. Therefore, the correct order of servicing using the C-SCAN scheduling algorithm is: 100−116−185−3−11−22−75−87.