Sjf Program In C

Diving Deep into SJF: A C Programming Journey

Imagine a bustling operating system, juggling multiple tasks simultaneously – printing documents, downloading files, running games. How does it decide which task gets attention first? One effective strategy is the Shortest Job First (SJF) scheduling algorithm. This article delves into the fascinating world of SJF, exploring its implementation in C, its strengths and weaknesses, and its real-world applications. We'll build a program together, step by step, to understand this fundamental concept in operating systems and process management.

Understanding the Shortest Job First (SJF) Algorithm

The Shortest Job First (SJF) algorithm, also known as the Shortest Process Next (SPN) algorithm, is a scheduling algorithm that prioritizes tasks with the shortest estimated burst time (the time required to complete the task). This approach minimizes the average waiting time for all processes. It aims to complete the quickest jobs first, leading to better overall system responsiveness.

There are two main variations of SJF:

Preemptive SJF: This version allows a shorter job to interrupt a currently running longer job. If a shorter job arrives while a longer job is running, the operating system preempts (interrupts) the longer job and starts the shorter one.
Non-preemptive SJF: This version does not interrupt running processes. A job only begins execution when the currently running job completes. Once a process begins, it runs to completion without interruption.

While preemptive SJF generally yields better results in terms of average waiting time, it involves more overhead due to context switching (saving and restoring the state of a process).

Implementing SJF in C: A Step-by-Step Guide

Let's build a non-preemptive SJF scheduler in C. This simplified version will illustrate the core concepts:

```c

include <stdio.h>

include <stdlib.h>

// Structure to represent a process
typedef struct {
int pid; // Process ID
int burst_time; // Burst time (execution time)
int waiting_time; // Waiting time
int turnaround_time; // Turnaround time (completion time)
} Process;

// Function to compare processes based on burst time
int compare(const void a, const void b) {
return ((Process )a)->burst_time - ((Process )b)->burst_time;
}

int main() {
int n;
printf("Enter the number of processes: ");
scanf("%d", &n);

Process processes[n];
for (int i = 0; i < n; i++) {
processes[i].pid = i + 1;
printf("Enter burst time for process %d: ", i + 1);
scanf("%d", &processes[i].burst_time);
processes[i].waiting_time = 0;
processes[i].turnaround_time = 0;
}

// Sort processes by burst time
qsort(processes, n, sizeof(Process), compare);

int waiting_time = 0;
int turnaround_time = 0;

// Calculate waiting and turnaround times
for (int i = 0; i < n; i++) {
processes[i].waiting_time = waiting_time;
processes[i].turnaround_time = waiting_time + processes[i].burst_time;
waiting_time += processes[i].burst_time;
turnaround_time += processes[i].turnaround_time;
}

// Print the results
printf("\nProcess\tBurst Time\tWaiting Time\tTurnaround Time\n");
for (int i = 0; i < n; i++) {
printf("%d\t\t%d\t\t%d\t\t%d\n", processes[i].pid, processes[i].burst_time, processes[i].waiting_time, processes[i].turnaround_time);
}

printf("\nAverage Waiting Time: %.2f\n", (float)waiting_time / n);
printf("Average Turnaround Time: %.2f\n", (float)turnaround_time / n);

return 0;
}
```

This code takes process burst times as input, sorts them using `qsort`, and then calculates and displays waiting and turnaround times for each process.

Real-World Applications of SJF

SJF finds practical applications in various scenarios:

Operating System Scheduling: Many operating systems use variations of SJF for task scheduling, especially in real-time systems where response time is critical (e.g., controlling robotic arms, managing industrial processes).
Job Scheduling in Servers: In server environments, SJF can optimize the execution of short jobs, improving overall server responsiveness.
Disk Scheduling: SJF principles can be applied to disk scheduling algorithms, prioritizing requests to nearby tracks to minimize seek time.
Resource Management: In resource-constrained systems, SJF can effectively manage resource allocation by prioritizing shorter tasks that require fewer resources.

Strengths and Weaknesses of SJF

Strengths:

Minimizes average waiting time: This is the primary advantage of SJF.
Improved system responsiveness: By completing short jobs quickly, the system responds faster to user requests.

Weaknesses:

Difficult to predict burst times accurately: In practice, accurately estimating burst times beforehand can be challenging. Inaccurate estimations can lead to poor performance.
Starvation of long processes: Long processes might experience significant delays if many short processes arrive continuously.
Implementation complexity (preemptive SJF): Preemptive SJF requires more complex implementation and adds context switching overhead.

Summary

This article explored the Shortest Job First scheduling algorithm, a vital concept in operating systems and process management. We detailed both preemptive and non-preemptive versions, highlighting their differences and practical applications. We also implemented a simplified non-preemptive SJF scheduler in C, demonstrating the algorithm's core logic. Understanding SJF is crucial for anyone interested in operating systems, systems programming, or performance optimization. While it possesses limitations, particularly concerning burst time prediction, its ability to minimize average waiting time makes it a valuable algorithm in various real-world scenarios.

FAQs

1. What is the difference between preemptive and non-preemptive SJF? Preemptive SJF allows a shorter job to interrupt a running longer job, while non-preemptive SJF does not interrupt running processes.

2. How can I improve the accuracy of burst time estimation in SJF? Techniques like historical data analysis and machine learning can help predict burst times more accurately.

3. What are some alternative scheduling algorithms? Other algorithms include First-Come, First-Served (FCFS), Round Robin, Priority Scheduling, and Multilevel Queue Scheduling.

4. Can SJF be used for real-time systems? Yes, particularly preemptive SJF is well-suited for real-time systems that require fast response times.

5. Is the C code provided a complete and robust implementation of SJF? No, it's a simplified example for educational purposes. A robust implementation would handle various edge cases and potentially use more sophisticated data structures.

Search Results:

SJF (Non-preemptive) Process Scheduling Algorithm Program in C/C++ 12 Nov 2019 · In the Shortest Job First (SJF) algorithm, if the CPU is available, it is assigned to the process that has the minimum next CPU burst. If the subsequent CPU bursts of two processes become the same, then FCFS scheduling is used to break the tie.

Shortest Job First (or SJF) CPU Scheduling Non-preemptive algorithm ... 17 Jan 2024 · The shortest job first (SJF) or shortest job next, is a scheduling policy that selects the waiting process with the smallest execution time to execute next. SJN, also known as Shortest Job Next (SJN), can be preemptive or non-preemptive.

C program for non-preemptive SJF CPU scheduling algorithm A different approach to CPU scheduling is the shortest-job-ﬁrst (SJF) scheduling algorithm. This algorithm associates with each process the length of the process’s next CPU burst. When the CPU is available, it is assigned to the process that has the smallest next CPU burst.

Simulating Shortest Job First (SJF) scheduling algorithm in C 22 Aug 2024 · Step 1: Start the process. Step 2: Accept the number of processes in the ready Queue. Step 3: For each process in the ready queue, assign the process id and accept the CPU burst time. Step 4: Start the ready queue, avoiding the shortest burst time by sorting according to lowest to highest burst time.

C Program for Shortest Job First (SJF) Scheduling Algorithm 14 Nov 2022 · Shortest Job First (SJF) is a type of disk scheduling algorithm in the operating system in which the processor executes the job first that has the smallest execution time. In the shortest Job First algorithm, the processes are scheduled according to …

SJF Scheduling Program in C - Sanfoundry This C program implement SJF scheduling algorithm to find the average waiting time and average turnaround time along with explanation and examples.

Shortest Job First or SJF CPU Scheduling - GeeksforGeeks 30 Jan 2025 · Shortest Job First (SJF) or Shortest Job Next (SJN) is a scheduling process that selects the waiting process with the smallest execution time to execute next. This scheduling method may or may not be preemptive. Significantly reduces the average waiting time for other processes waiting to be executed.

SJF scheduling algorithm in C · GitHub SJF scheduling algorithm in C. GitHub Gist: instantly share code, notes, and snippets.

Enzalutamide in patients with high-risk biochemically recurrent ... 26 Mar 2025 · Department of Urology and Research Program in Systems Oncology, University of Helsinki, Helsinki, Finland ... SJF reports consulting for Astellas Pharma Inc., AstraZeneca, Bayer, Eli Lilly, Exact ...

Shortest Job First Scheduling in C Programming | Edureka 29 Mar 2022 · This article will provide you with a detailed and comprehensive knowledge of Shortest Job First Scheduling in C Programming with examples.

Shortest Job First Scheduling Algorithm in C with Gantt Chart 9 Feb 2016 · The following program is a simulation of Shortest Job First scheduling algorithm. In this program, processes are sorted by their burst time in ascending order. To sort the list of process, I used Bubble Sort algorithm here.

What is the SJF scheduling program in C? | by Mayanknegi 17 Oct 2023 · In this blog article, we will learn how to build the SJF scheduling algorithm in the C programming language. The algorithm and its operation will be covered first, and then the specifics of its...

C program on the SJF(Shortest job first) preemptive Sjf scheduling can be either preemptive or non-preemptive. IN SJF CPU is assigned to the process that has the smallest next CPU Burst time. If the next CPU Burst of two process is the same then FCFS scheduling is used to break the tie. This process give the minimum average waiting time for a given processes. Code:-

C Program to Implement SJF CPU Scheduling Algorithm scanf("%s%d%d",pn[i],&at[i],&et[i]); for(i=0; i<n; i++) for(j=0; j<n; j++) if(et[i]<et[j]) temp=at[i]; at[i]=at[j]; at[j]=temp; temp=et[i]; et[i]=et[j]; et[j]=temp; strcpy(t,pn[i]); strcpy(pn[i],pn[j]); strcpy(pn[j],t); for(i=0; i<n; i++) if(i==0) st[i]=at[i]; else. st[i]=ft[i-1]; …

SJF Scheduling Program in C - The Crazy Programmer Here you will get C program for shortest job first (sjf) scheduling algorithm. In shortest job first scheduling algorithm, the processor selects the waiting process with the smallest execution time to execute next.

Program for Shortest Job First (or SJF) CPU Scheduling 24 Mar 2023 · The shortest job first (SJF) or shortest job next, is a scheduling policy that selects the waiting process with the smallest execution time to execute next. SJN, also known as Shortest Job Next (SJN), can be preemptive or non-preemptive.

SJF Scheduling Program in C 29 Dec 2022 · One CPU scheduling strategy involves giving priority to the shortest jobs first, using an algorithm that depends on the burst time of processes. Simply put, processes with lower burst times are executed first. The term "Shortest Job Next" (SJN) is …

Shortest Job First Program in C (SJF Scheduling) Today we will learn the Shortest Job First Program in C. So, before start learning, you should have a little bit knowledge about Shortest job first. What is Shortest Job First? 1. Shortest Job First Program in C (Non-preemptive) 2. Shortest Job First Program in C (Preemptive) What is Shortest Job First?

Shortest Job First (SJF) Scheduling algorithm Program in C Shortest Job First (SJF) is a CPU Scheduling algorithm in which allocation of CPU is based on burst time. The job having less burst time will get scheduled first.

C Program for Shortest Job First (SJF) Scheduling Algorithm 31 Oct 2019 · Here you will get a C program for the shortest job first (sjf) scheduling algorithm. In the shortest job first scheduling algorithm, the processor chooses the. holding up process with the littlest execution time to execute straight away. Beneath I have shared the C program for this algorithm. Program.

Understanding Shortest Job First Scheduling in C Programming 14 Dec 2023 · Shortest Job First scheduling, also known as Shortest Job Next (SJN) or Shortest Job First (SJF), is a non-preemptive SJF scheduling algorithm that selects the process with the smallest burst time or execution time to execute first.