Write a C program to implement the various process scheduling mechanisms such as SJF Scheduling.

Write a C program to implement the various process scheduling mechanisms such as SJF Scheduling.

Description of SJF Scheduling: Shortest Job First: The criteria of this algorithm are which process having the smallest CPU burst, CPU is assigned to that next process. If two process having the same CPU burst time FCFS is used to break the tie.

Algorithm for SJF:

Step 1: Start the process

Step 2: Accept the number of processes in the ready Queue

Step 3: For each process in the ready Q, assign the process id and accept the CPU burst time

Step 4: Start the Ready Q according to the shortest Burst time by sorting according to lowest to

highest burst time.

Step 5: Set the waiting time of the first process as ‘0’ and its turnaround time as its burst time.

Step 6: For each process in the ready queue, calculate

(a) Waiting time for process(n)= waiting time of process (n-1) + Burst time of process(n-1)

(b) Turn around time for Process(n)= waiting time of Process(n)+ Burst time for process(n)

Step 6: Calculate

(c) Average waiting time = Total waiting Time / Number of process

(d) Average Turnaround time = Total Turnaround Time / Number of process

Step 7: Stop the process

/* Program to Simulate Shortest Job First CPU Scheduling Algorithm */

Program Code:

#include<stdio.h>

#include<conio.h>

#include<string.h>

void main()

{

int i,j,n,bt[10],compt[10], wt[10],tat[10],temp;

float sumwt=0.0,sumtat=0.0,avgwt,avgtat;

clrscr();

printf("Enter number of processes: ");

scanf("%d",&n);

printf("Enter the burst time of %d process\n", n);

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

{

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

}

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

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

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

{

temp=bt[i];

bt[i]=bt[j];

bt[j]=temp;

}

compt[0]=bt[0];

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

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

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

{

tat[i]=compt[i];

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

sumtat+=tat[i];

sumwt+=wt[i];

}

avgwt=sumwt/n;

avgtat=sumtat/n;

printf("------------------------------\n");

printf("Bt\tCt\tTat\tWt\n");

printf("------------------------------\n");

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

{

printf("%2d\t%2d\t%2d\t%2d\n",i,bt[i],compt[i],tat[i],wt[i]);

}

printf("------------------------------\n");

printf(" Avgwt = %.2f\tAvgtat = %.2f\n",avgwt,avgtat);

printf("-------------------------------\n");

getch();

}

Program Output:

Enter number of processes: 4

Enter the burst time of 4 process

6 8 7 3

------------------------------------

Bt Ct Tat Wt

------------------------------------

3 3 3 0

6 9 9 3

7 16 16 9

8 24 24 16

--------------------------------------

Avgwt = 7.00 Avgtat = 13.00