Non preemptive scheduling – Solved Gate%20 Question Papers

Lui Kreyszig

3 months ago

https://www.gyanodhan.com/video/7B7.%20GATE%20CSEIT/Operating%20System/402.%20Non%20preemptive%20scheduling%20-%20Solved%20Gate%20%20Question%20Papers.mp4

Absolutely! Here’s a complete breakdown of Non-Preemptive Scheduling with a solved GATE-style question, including explanation, table, and Gantt chart — tailored for GATE CSE/IT aspirants.

Contents

1 Topic: Non-Preemptive Scheduling
2 What is Non-Preemptive Scheduling?
- 2.1 Common Non-Preemptive Scheduling Algorithms:
3 Solved GATE-Style Question: SJF (Non-Preemptive)
4 Summary:
5 Key Concepts to Remember:
- 5.1 Non preemptive scheduling – Solved Gate%20 Question Papers
- 5.2 Operating System Sl.No. Name of the Topic 1. Process …

Topic: Non-Preemptive Scheduling

Subject: Operating System
GATE Relevance: High
Type: Numerical-based Questions (Process Scheduling)

What is Non-Preemptive Scheduling?

In Non-Preemptive Scheduling, once a process starts executing on the CPU, it cannot be stopped until it completes.
The CPU is assigned only after the current process finishes.
This contrasts with Preemptive scheduling, where the CPU can be taken away by a higher-priority task.

Common Non-Preemptive Scheduling Algorithms:

Algorithm	Description
FCFS (First Come First Serve)	Processed in order of arrival
SJF (Shortest Job First)	Process with shortest burst time first
Priority Scheduling (Non-preemptive)	Highest priority (lowest number) runs first

Solved GATE-Style Question: SJF (Non-Preemptive)

Question:
Consider the following processes:

Process	Arrival Time	Burst Time
P1	0 ms	8 ms
P2	1 ms	4 ms
P3	2 ms	9 ms
P4	3 ms	5 ms

Use Non-Preemptive SJF Scheduling.
Find the Average Waiting Time and Average Turnaround Time.

Step 1: Gantt Chart (SJF – Shortest Job First)

Initial time = 0, only P1 has arrived ⇒ Execute P1
At time 8, P2, P3, P4 have arrived
Shortest burst time among them = P2 (4ms)
Next = P4 (5ms)
Then = P3 (9ms)

Gantt Chart:

Step 2: Calculate Completion, Turnaround, and Waiting Times

Process	Arrival Time	Burst Time	Completion Time	Turnaround Time (CT – AT)	Waiting Time (TAT – BT)
P1	0	8	8	8	0
P2	1	4	12	11	7
P3	2	9	26	24	15
P4	3	5	17	14	9

Final Answers:

Average Waiting Time = (0 + 7 + 15 + 9) / 4 = 7.75 ms
Average Turnaround Time = (8 + 11 + 24 + 14) / 4 = 14.25 ms

Summary:

Metric	Value
Avg Waiting Time	7.75 ms
Avg Turnaround Time	14.25 ms

Key Concepts to Remember:

In Non-preemptive SJF, CPU waits for a process to finish before giving it to the next.
Always update available processes at each CPU idle time.
For equal burst times, use arrival time as tie-breaker.

Want more GATE previous year solved papers for OS scheduling?
I can generate a full PDF set, practice quizzes, or custom short tricks — just let me know what format you prefer!

<img src="https://s.w.org/images/core/emoji/13.0.1/72x72/1f3af.png" alt="🎯" class="wp-smiley amp-wp-843f19c" width="72" height="72" data-amp-original-style="height: 1em; max-height: 1em;"> Topic: Non-Preemptive Scheduling

<img src="https://s.w.org/images/core/emoji/13.0.1/72x72/1f4d8.png" alt="📘" class="wp-smiley amp-wp-843f19c" width="72" height="72" data-amp-original-style="height: 1em; max-height: 1em;"> What is Non-Preemptive Scheduling?

<img src="https://s.w.org/images/core/emoji/13.0.1/72x72/2705.png" alt="✅" class="wp-smiley amp-wp-843f19c" width="72" height="72" data-amp-original-style="height: 1em; max-height: 1em;"> Common Non-Preemptive Scheduling Algorithms:

<img src="https://s.w.org/images/core/emoji/13.0.1/72x72/1f4dd.png" alt="📝" class="wp-smiley amp-wp-843f19c" width="72" height="72" data-amp-original-style="height: 1em; max-height: 1em;"> Solved GATE-Style Question: SJF (Non-Preemptive)

<img src="https://s.w.org/images/core/emoji/13.0.1/72x72/1f9ee.png" alt="🧮" class="wp-smiley amp-wp-843f19c" width="72" height="72" data-amp-original-style="height: 1em; max-height: 1em;"> Step 1: Gantt Chart (SJF – Shortest Job First)

<img src="https://s.w.org/images/core/emoji/13.0.1/72x72/1f4ca.png" alt="📊" class="wp-smiley amp-wp-843f19c" width="72" height="72" data-amp-original-style="height: 1em; max-height: 1em;"> Gantt Chart:

<img src="https://s.w.org/images/core/emoji/13.0.1/72x72/1f4cb.png" alt="📋" class="wp-smiley amp-wp-843f19c" width="72" height="72" data-amp-original-style="height: 1em; max-height: 1em;"> Step 2: Calculate Completion, Turnaround, and Waiting Times

<img src="https://s.w.org/images/core/emoji/13.0.1/72x72/1f9e0.png" alt="🧠" class="wp-smiley amp-wp-843f19c" width="72" height="72" data-amp-original-style="height: 1em; max-height: 1em;"> Final Answers:

<img src="https://s.w.org/images/core/emoji/13.0.1/72x72/1f4e6.png" alt="📦" class="wp-smiley amp-wp-843f19c" width="72" height="72" data-amp-original-style="height: 1em; max-height: 1em;"> Summary:

<img src="https://s.w.org/images/core/emoji/13.0.1/72x72/1f4a1.png" alt="💡" class="wp-smiley amp-wp-843f19c" width="72" height="72" data-amp-original-style="height: 1em; max-height: 1em;"> Key Concepts to Remember: