FCFS disk scheduling in Operating Systems - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding FCFS Disk Scheduling

What is the main characteristic of the First-Come, First-Served (FCFS) disk scheduling algorithm?

A It prioritizes requests based on their priority level.

B It always selects the request closest to the current head position.

C It processes disk requests in the order they arrive without reordering.

D It reorders requests to minimize total seek time.

💡 Hint

Think about how requests are handled as they come in.

FCFS processes disk requests strictly in the order they arrive, without any reordering or optimization.

🚀 Application

intermediate

Calculating Total Head Movement in FCFS

Given the initial head position at 50 and the request queue: 82, 170, 43, 140, 24, what is the total head movement using FCFS scheduling?

A 344

B 230

C 208

D 460

💡 Hint

Calculate the absolute distance between consecutive requests starting from the initial head position.

Total head movement is the sum of distances between consecutive requests in the order they arrive.

🔍 Analysis

advanced

Identifying Drawbacks of FCFS Disk Scheduling

Which of the following is a significant drawback of the FCFS disk scheduling algorithm?

A It can cause long wait times due to lack of optimization.

B It always minimizes seek time effectively.

C It prioritizes urgent requests over others.

D It requires complex calculations to reorder requests.

💡 Hint

Consider how FCFS handles requests without reordering.

FCFS does not optimize the order of requests, which can lead to long wait times and inefficient head movement.

❓ Comparison

advanced

Comparing FCFS with Other Disk Scheduling Algorithms

Compared to algorithms like SSTF or SCAN, how does FCFS generally perform in terms of average seek time?

A FCFS always has the lowest average seek time.

B FCFS usually has higher average seek time than SSTF or SCAN.

C FCFS and SSTF have the same average seek time.

D FCFS performs better than SCAN in all cases.

💡 Hint

Think about how FCFS processes requests without optimization.

FCFS does not optimize head movement, so it usually results in higher average seek times compared to SSTF or SCAN.

❓ Reasoning

expert

Predicting FCFS Behavior with Specific Request Patterns

If the disk head starts at position 100 and the request queue is 105, 95, 110, 90, 115, what will be the total head movement using FCFS scheduling?

A 75

B 50

C 40

D 30

💡 Hint

Calculate the sum of absolute differences between consecutive requests starting from 100.

Calculate distances: |100-105|=5, |105-95|=10, |95-110|=15, |110-90|=20, |90-115|=25; total = 5+10+15+20+25 = 75