Disk Scheduling

Question

How does LOOK algorithm decides that this is the last request? What technique is used to determine that after this request, instead of going to the end of disk, the direction should be changed?

Comments

One way is to feed the algorithm with a an array of the records ,so when the RW head reaches the largest or lowest number it changes direction

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But requests are dynamic, so how can you possibly determine the array of requests. Moreover how it will decide that it this the largest number/ lowest number without traversing the whole array?

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check this out! here is the link to a c implementation of the scheduling algorithms 

https://codereview.stackexchange.com/questions/48326/disk-scheduling-algorithm

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Thanks.

But it is a program which intends to calculate head movements only.

My concern is different.