SJF Scheduling Program in C

Here you will learn SJF Scheduling and, the program code of SJF Scheduling Program in C programming language.

Table of Contents

sjf scheduling in os

Shortest Job First (SJF) is a scheduling algorithm used in operating systems to manage processes. It is a non–preemptive algorithm, which means that once a process has started running, it cannot be interrupted until it has completed its task. The aim of SJF is to minimize the average waiting time of processes.

The algorithm works by sorting the processes by their burst time and then scheduling them in the order of shortest burst time first. This ensures that the processes with the shortest burst time are executed first and thus the average waiting time is minimized.

SJF scheduling can be used in preemptive and non-preemptive mode. The preemptive mode of Shortest Job First is called as Shortest Remaining Time First (SRTF).

Non-Preemptive SJF

Non-preemptive SJF is a scheduling algorithm that works by having the process with the shortest job run first. This means that the process with the shortest job will run until it is completed before the next process can start. This algorithm helps reduce waiting time and is known to be one of the most efficient scheduling algorithms.

Process Queue	Burst time	Arrival time
P1	6	2
P2	2	5
P3	8	1
P4	3	0
P5	4	4

Wait time
P4= 0-0=0
P1= 3-2=1
P2= 9-5=4
P5= 11-4=7
P3= 15-1=14

Average Waiting Time = 0+1+4+7+14/5 = 26/5 = 5.2

Preemptive SJF

In Preemptive SJF Scheduling, jobs are processed in queue as they come. A process with shortest burst time start execution. If a process has a shorter burst duration, it takes the place of the one that is now running and gets a CPU cycle for the shorter task.

Process with following table:

Process Queue	Burst time	Arrival time
P1	6	2
P2	2	5
P3	8	1
P4	3	0
P5	4	4

Wait time
P4= 0-0=0
P1= (3-2) + 6 =7
P2= 5-5 = 0
P5= 4-4+2 =2
P3= 15-1 = 14

Average Waiting Time = 0+7+0+2+14/5 = 23/5 =4.6

SJF scheduling example

//SJF Scheduling Program in C

#include<stdio.h>

#include<conio.h>

void main()

{

int bt[20],p[20],wt[20],tat[20],i,j,n,total=0,pos,temp;

float avg_wt,avg_tat;

printf("\nEnter number of process:");

scanf("%d",&n);

printf("\nEnter Burst Time:n");

for(i=0;i<n;i++)

{

printf("p%d:",i+1);

scanf("%d",&bt[i]);

p[i]=i+1;

}

for(i=0;i<n;i++)

{

pos=i;

for(j=i+1;j<n;j++)

{

if(bt[j]<bt[pos])

pos=j;

}

temp=bt[i];

bt[i]=bt[pos];

bt[pos]=temp;

temp=p[i];

p[i]=p[pos];

p[pos]=temp;

}

wt[0]=0;

for(i=1;i<n;i++)

{

wt[i]=0;

for(j=0;j<i;j++)

wt[i]+=bt[j];

total+=wt[i];

}

avg_wt=(float)total/n;

total=0;

printf("\nProcesst Burst Time \tWaiting Time\tTurnaround Time");

for(i=0;i<n;i++)

{

tat[i]=bt[i]+wt[i];

total+=tat[i];

printf("\np%d\t\t %d\t\t %d\t\t\t%d",p[i],bt[i],wt[i],tat[i]);

}

avg_tat=(float)total/n; //average turnaround time

printf("\n\nAverage Waiting Time=%f",avg_wt);

printf("\nAverage Turnaround Time=%f\n",avg_tat);

}

Output

Read Also

Round Robin Scheduling Program in C

SJF Scheduling Program in C

SJF Scheduling Program in C

sjf scheduling in os

Non-Preemptive SJF

Preemptive SJF

SJF scheduling example

2 thoughts on “SJF Scheduling Program in C”

Leave a Comment Cancel Reply

SJF Scheduling Program in C

SJF Scheduling Program in C

sjf scheduling in os

Non-Preemptive SJF

Preemptive SJF

SJF scheduling example

Social Share

Read More

2 thoughts on “SJF Scheduling Program in C”

Leave a Comment Cancel Reply