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Suppose that the head of a moving head disk with 192 tracks(0-191), is currently serving a request at track 80 and has just finished at track 62. The queue of the request is kept in FIFO order: 119, 58, 114, 28, 111, 55, 103, 30, 75. What is the total no of tracks traversed by head movements needed to satisfy these request for the Elevator disk-scheduling algorithm?

a. 143

b. 130

c. 177

d. 547

### 1 comment

Not getting any of the above as ans. Acc to question, the direction of the head movement is towards right and accordingly ans should be 340

80--->103--->111--->114--->119--->191--->75--->58--->55--->30--->28

Head Movements = (191-80) + (191-28) = 274. (Correct Answer)

What they considered:

80--->103--->111--->114--->119--->75--->58--->55--->30--->28

Head Movements = (119-80) + (119-28)  = 130.   , here, option (b)  is correct.(Acc. to them)

### 1 comment

Yes, they have asked about elevator algorithm (SCAN) and they have given answer according to Look algorithm

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