C-SCAN (circular SCAN) in Operating Systems - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to describe the direction of the disk arm in C-SCAN.

Operating Systems

The disk arm moves in one direction until it reaches the end, then it [1] to the beginning.

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

Ajumps

Breverses

Cstops

Dslows

Attempts:

3 left

💡 Hint

Common Mistakes

Thinking the arm reverses direction like in SCAN.

Assuming the arm stops at the end.

In C-SCAN, the disk arm moves in one direction and when it reaches the end, it jumps back to the beginning without servicing requests on the return.

2fill in blank

medium

Complete the code to explain the main advantage of C-SCAN over SCAN.

Operating Systems

C-SCAN provides a more uniform wait time by servicing requests in a [1] direction only.

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

Asingle

Brandom

Cboth

Dreverse

Attempts:

3 left

💡 Hint

Common Mistakes

Thinking C-SCAN services requests in both directions.

Confusing C-SCAN with SCAN.

C-SCAN services requests in a single direction only, which helps provide a more uniform wait time compared to SCAN that moves back and forth.

3fill in blank

hard

Fix the error in the description of C-SCAN's movement.

Operating Systems

In C-SCAN, the disk arm moves from the start to the end and then [1] back servicing requests on the return.

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

Areverses

Bstops

Cjumps

Dpauses

Attempts:

3 left

💡 Hint

Common Mistakes

Saying the arm reverses and services requests on the return.

Assuming the arm stops at the end.

C-SCAN moves the arm from start to end servicing requests, then jumps back to the start without servicing requests on the return.

4fill in blank

hard

Fill both blanks to complete the C-SCAN algorithm description.

Operating Systems

C-SCAN moves the disk arm from [1] to [2], servicing requests only in this direction.

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

Astart

Bmiddle

Cend

Drandom

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing middle or random as start or end points.

Confusing the direction of movement.

C-SCAN moves the disk arm from the start to the end of the disk, servicing requests only in this direction before jumping back.

5fill in blank

hard

Fill all three blanks to complete the C-SCAN scheduling code snippet.

Operating Systems

requests = sorted(requests)
current_pos = [1]
for req in requests:
    if req >= current_pos:
        service(req)
current_pos = [2]
for req in requests:
    if req < current_pos:
        service(req)
current_pos = [3]

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

A0

Bmax_track

Dmiddle

Attempts:

3 left

💡 Hint

Common Mistakes

Using middle or random values instead of 0 or max_track.

Not resetting current_pos correctly.

The C-SCAN algorithm starts servicing requests from the current position (0), moves to the max track, then jumps back to 0 to service remaining requests.