SSTF (Shortest Seek Time First) in Operating Systems - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the next disk request chosen by SSTF.

Operating Systems

next_request = min(requests, key=lambda r: abs(r - [1]))

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

Acurrent_head_position

Brequest

Crequests

Dmin

Attempts:

3 left

💡 Hint

Common Mistakes

Using the request variable inside the abs() instead of the current head position.

Confusing the list of requests with the current position.

The SSTF algorithm selects the request closest to the current head position. Here, current_head_position is used to find the minimum distance.

2fill in blank

medium

Complete the code to remove the served request from the list after SSTF selects it.

Operating Systems

requests.remove([1])

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

Amin

Bcurrent_head_position

Crequests

Dnext_request

Attempts:

3 left

💡 Hint

Common Mistakes

Removing the current head position instead of the request.

Trying to remove the entire list of requests.

After serving a request, SSTF removes the next_request from the list to avoid serving it again.

3fill in blank

hard

Fix the error in updating the current head position after serving a request.

Operating Systems

current_head_position = [1]

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

Anext_request

Bmax(requests)

Cmin(requests)

Drequests[0]

Attempts:

3 left

💡 Hint

Common Mistakes

Setting the head to the first or last request in the list instead of the served request.

Not updating the head position at all.

The current head position should be updated to the next_request that was just served, not the minimum or maximum of remaining requests.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps each request to its distance from the current head position.

Operating Systems

distances = {r: abs(r [1] current_head_position) for r in requests if r [2] current_head_position}

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

A-

B>

C<

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of subtraction for distance.

Filtering requests less than the current head position.

The distance is calculated by subtracting the current head position from each request (r - current_head_position). The filter keeps requests greater than the current head position.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps each request to its distance from the current head position, considering requests both less and greater than the head.

Operating Systems

distances = {r: abs(r [1] current_head_position) for r in requests if r [2] current_head_position or r [3] current_head_position}

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

A-

B>

C<

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of subtraction.

Filtering only requests greater than the head.

The distance is calculated by subtracting the current head position from each request (r - current_head_position). The filter includes requests both greater than and less than the current head position.