FCFS disk scheduling in Operating Systems - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does FCFS stand for in disk scheduling?

FCFS stands for First-Come, First-Served. It is a simple disk scheduling algorithm where requests are processed in the order they arrive.

beginner

How does FCFS disk scheduling decide which request to serve next?

FCFS serves disk requests in the exact order they arrive, without reordering or prioritizing any request.

intermediate

What is a major drawback of FCFS disk scheduling?

A major drawback is that it can cause long waiting times if requests are far apart on the disk, leading to inefficient disk arm movement.

beginner

Explain with a simple example how FCFS disk scheduling works.

If the disk head is at track 50 and requests come for tracks 55, 58, and 52 in that order, FCFS will move the head to 55 first, then 58, then 52, following the arrival order.

beginner

Is FCFS disk scheduling fair? Why or why not?

Yes, FCFS is fair because it serves requests in the order they arrive, so no request is skipped or delayed unfairly.

What is the main principle of FCFS disk scheduling?

A Serve the closest request first

B Serve requests in reverse order

C Serve the request with the shortest seek time

D Serve requests in the order they arrive

FCFS serves disk requests in the order they arrive, without reordering.

Which of the following is a disadvantage of FCFS disk scheduling?

A It can cause long wait times due to inefficient head movement

B It always prioritizes the closest request

C It requires complex calculations

D It ignores the order of requests

FCFS can cause long wait times because it does not optimize the order of requests.

If the disk head is at track 30 and requests arrive for tracks 40, 10, and 50 in that order, which track will FCFS move to first?

A Track 40

B Track 30

C Track 50

D Track 10

FCFS serves requests in arrival order, so it moves to track 40 first.

Is FCFS disk scheduling considered fair to all requests?

A No, it serves requests randomly

B Yes, because it serves requests in arrival order

C No, it favors requests near the current head position

D Yes, because it serves the shortest request first

FCFS is fair since it processes requests in the order they arrive.

Which disk scheduling algorithm is simpler to implement?

A SCAN

B Shortest Seek Time First

C FCFS

D C-SCAN

FCFS is the simplest disk scheduling algorithm as it just follows request arrival order.

Describe how FCFS disk scheduling works and mention one advantage and one disadvantage.

Think about the order of requests and how the disk head moves.

Explain why FCFS disk scheduling might lead to inefficient disk arm movement.

Consider how the disk head travels between requests.