LOOK and C-LOOK variants in Operating Systems - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the main purpose of the LOOK disk scheduling algorithm.

Operating Systems

The LOOK algorithm moves the disk arm towards the last request in one direction and then [1].

Drag options to blanks, or click blank then click option'

Aignores requests

Bstops permanently

Creverses direction

Dmoves randomly

Attempts:

3 left

💡 Hint

Common Mistakes

Assuming the arm stops permanently after reaching the last request.

Thinking the arm moves randomly without direction.

The LOOK algorithm moves the disk arm towards the last request in one direction and then reverses direction to service requests on the return path.

2fill in blank

medium

Complete the code to describe how C-LOOK differs from LOOK.

Operating Systems

Unlike LOOK, C-LOOK moves the disk arm in one direction and then [1] to the beginning without servicing requests on the return.

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Ajumps back

Breverses direction

Cstops

Dservices all requests

Attempts:

3 left

💡 Hint

Common Mistakes

Thinking C-LOOK reverses direction like LOOK.

Assuming C-LOOK services requests on the return trip.

C-LOOK moves the disk arm in one direction servicing requests, then jumps back to the beginning without servicing requests on the return.

3fill in blank

hard

Fix the error in the statement about LOOK algorithm behavior.

Operating Systems

LOOK algorithm always moves the disk arm to the very end of the disk before [1].

Drag options to blanks, or click blank then click option'

Areversing direction

Bservicing requests

Cstopping permanently

Dignoring requests

Attempts:

3 left

💡 Hint

Common Mistakes

Assuming LOOK always goes to the disk's end.

Confusing LOOK with SCAN algorithm.

The LOOK algorithm does not move to the very end of the disk unless there is a request there; it moves only as far as the last request before reversing direction.

4fill in blank

hard

Fill both blanks to complete the description of C-LOOK's disk arm movement.

Operating Systems

C-LOOK moves the disk arm in one direction until the last request, then [1] to the [2] request without servicing requests on the way back.

Drag options to blanks, or click blank then click option'

Ajumps back

Breverses

Cbeginning

Dend

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'reverses' instead of 'jumps back'.

Selecting 'end' instead of 'beginning' for the return point.

C-LOOK moves the disk arm in one direction until the last request, then jumps back to the beginning request without servicing requests on the return.

5fill in blank

hard

Fill both blanks to complete the dictionary comprehension representing LOOK algorithm's request servicing order.

Operating Systems

look_order = {req: req for req in requests if req {BLANK_2}} current_pos and req {{BLANK_2}} direction_limit{{D}}

Drag options to blanks, or click blank then click option'

A{

B>

C<

D}

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong comparison operators for filtering requests.

Omitting braces in the comprehension.

The dictionary comprehension starts with '{', filters requests greater than current position and less than direction limit, and ends with '}'.