Why FCFS disk scheduling in Operating Systems? - Purpose & Use Cases

The Big Idea

What if your computer's disk had to jump all over the place just to read your files? FCFS keeps it simple and fair!

The Scenario

Imagine you have a stack of papers on your desk, and you need to find specific pages scattered throughout. You decide to pick them up in the exact order they appear on the desk, without thinking about their location. This is like manually handling disk requests as they come, without any planning.

The Problem

Doing this manually means you might jump back and forth across the desk, wasting time moving your hand unnecessarily. Similarly, handling disk requests in the order they arrive can cause the disk head to move a lot, slowing down the system and increasing wait times.

The Solution

FCFS (First-Come, First-Served) disk scheduling processes requests in the order they arrive, just like picking papers in sequence. This simple method ensures fairness and is easy to implement, avoiding confusion about which request to handle next.

Before vs After

✗ Before

requests = [55, 58, 39, 18, 90]
for req in requests:
    move_disk_head(req)

✓ After

requests = [55, 58, 39, 18, 90]
# FCFS processes requests as they come
for req in requests:
    move_disk_head(req)

What It Enables

FCFS disk scheduling enables a straightforward and fair way to handle disk requests, ensuring every request is served in the order it arrives without complex decision-making.

Real Life Example

Think of a queue at a coffee shop where customers are served in the order they arrive. FCFS disk scheduling works the same way, serving disk requests one by one as they come.

Key Takeaways

FCFS handles disk requests in arrival order.

It is simple and fair but may cause longer wait times due to head movement.

Useful as a basic scheduling method in operating systems.