Solution:Given the queue of requests in FIFO order: 86, 147, 91, 177, 94, 150, 102, 175, 130.
Sorted requests : 86, 91, 94, 102, 130, 147, 150, 175, 177.
Current nead position : 143
Now, applying the SCAN algorithm-
Total head movements = (147 – 143) + (150 – 147) +
(175 – 150) + (177 – 175) + (177 – 86) + (91-86)+ (94 –
91) + (102 – 94) + (130 – 102)
= 4 + 3 + 25 + 2 + 91 + 5 + 3 + 8 + 28
= 169 tracks
Therefore, the total number of head movements
required so satisfy these requests for the SCAN
algorithm with 169 cylinders is 169 tracks.