Write a C program to implement the Priority Scheduling mechanisms.

Write a C program to implement the Priority Scheduling mechanisms.

Description of Priority Scheduling:

Priority Scheduling: These are of two types.

One is the internal priority, second is the external priority. The cpu is allocated to the process with the highest priority. Equal priority processes are scheduled in the FCFS order. Priorities are generally some fixed range of numbers such as 0 to 409. The low numbers represent high priority.

Algorithm for Priority Scheduling:

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: Sort the ready queue according to the priority number.

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

Step 6: For each process in the Ready Q calculate

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

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

Step 7: Calculate

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

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

Step 8: Stop the process

/* Program to Simulate Priority CPU Scheduling Algorithm */

Program Code:

#include<stdio.h>

#include<conio.h>

void main()

{

int i,j,n,bt[10],p[10],compt[10], wt[10],tat[10],temp1,temp2;

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]);

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

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

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

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

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

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

{

temp1=bt[i];

bt[i]=bt[j];

bt[j]=temp1;

temp2=p[i];

p[i]=p[j];

p[j]=temp2;

}

compt[0]=bt[0]; wt[0]=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",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 5 3 5

Enter the priority of 4 process

4 2 6 3

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

Bt Ct Tat Wt

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

5 5 5 0

5 10 10 5

6 16 16 10

3 19 19 16

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

Avgwt = 7.75 Avgtat = 12.50