SCAN and CSCAN algorithm in Operating system

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I've gone through some notes and coursebook regarding the drawing of SCAN and CSCAN algorithm, given a queue of requests and the position of head starts in the example.

I wonder if it is a must to move from the starting position to the position zero first, then the head reverse its direction to another end (which is the non-zero side)...

Is it OK if I move from the starting point to the non-zero side first (if the starting point given is closer to the non-zero side eg.124). After that, the head reverse it's direction back to the side of position zero.

It depends on the given direction of disk arm movement.

You can choose either Towards the beginning of the disk or Towards the end of the disk.

There is a Github project about Disk Scheduling Program, take a look if you want to know more about it