Write a c program to implement shortest job first scheduling algorithms non-preemptive

Write a c program to implement shortest job first scheduling algorithms non-preemptive

Algorithm:

1.       Start

2.      Declare the array size p[20], bt[20], wt[20], tat[20], i, k, n, temp; float wtavg, tatavg;

3.      Read the number of processes to be inserted

4.      Read the Burst times of processes

5.      Sort the Burst times in ascending order and process with shortest burst time is first executed.

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

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

if(bt[i]>bt[k])

{   

temp=bt[i];

bt[i]=bt[k];

bt[k]=temp;

temp=p[i];

p[i]=p[k];

p[k]=temp;

}

6.      waiting time for first process will be zero

wt[0] = wtavg = 0;

tat[0] = tatavg = bt[0];

7.      calculate waiting time and turnaround time

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

{

wt[i] = wt[i-1] +bt[i-1];

tat[i] = tat[i-1] +bt[i];

wtavg = wtavg + wt[i];

tatavg = tatavg + tat[i];

}

8.      Calculate the average waiting time and average turnaround time.

awt=wtavg/n;

atat=tatavg/n;

9.      Display the values

10.  Stop

source code:

#include<stdio.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("Enter 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;           //contains process number

    }

    //sorting burst time in ascending order using selection sort

    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;            //waiting time for first process will be zero

    //calculate waiting time

    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;      //average waiting time

    total=0;

    printf("\nProcess\t    Burst Time    \tWaiting Time\tTurnaround Time");

    for(i=0;i<n;i++)

    {

        tat[i]=bt[i]+wt[i];     //calculate turnaround time

        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: