Here you will get a C and C++ program for priority scheduling algorithm.
What is Priority Scheduling Algorithm?
In priority scheduling algorithm each procedure has a priority related with it and as
each procedure hits the line, it is put away independent on its priority so process with higher priority is managed first.
It ought to be noticed that equivalent priority procedure are planned in FCFS request.
To anticipate high priority forms from running uncertainly the scheduler may diminish
the priority of the right now running procedure at each clock tick (i.e., at each clock interfere).
In the event that this activity makes its priority dip under that of the following most noteworthy procedure,
a procedure switch happens. On the other hand, each procedure might be relegated a most extreme time
quantum that it is permitted to run. At the point when this quantum is spent, the following most noteworthy priority procedure is allowed to run.
Impediments
The issue happens when the working framework gives a specific assignment an extremely low priority,
so it sits in the line for a bigger measure of time, not being managed by the CPU. On the off chance
that this procedure is something the client needs, there could be a long pause, this procedure is known as “Starvation” or “Unbounded Blocking”.
Arrangement
Many working frameworks use a system called “maturing”, in which a low priority process gradually
gains priority after some time as it sits in the line. Regardless of whether the priority of the procedure is low, there is a surety of its execution.
C program
#include<stdio.h>
int main()
{
int bt[20],p[20],wt[20],tat[20],pr[20],i,j,n,total=0,pos,temp,avg_wt,avg_tat;
printf("Enter Total Number of Process:");
scanf("%d",&n);
printf("\nEnter Burst Time and Priority\n");
for(i=0;i<n;i++)
{
printf("\nP[%d]\n",i+1);
printf("Burst Time:");
scanf("%d",&bt[i]);
printf("Priority:");
scanf("%d",&pr[i]);
p[i]=i+1; //contains process number
}
//sorting burst time, priority and process number in ascending order using selection sort
for(i=0;i<n;i++)
{
pos=i;
for(j=i+1;j<n;j++)
{
if(pr[j]<pr[pos])
pos=j;
}
temp=pr[i];
pr[i]=pr[pos];
pr[pos]=temp;
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 is 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=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=total/n; //average turnaround time
printf("\n\nAverage Waiting Time=%d",avg_wt);
printf("\nAverage Turnaround Time=%d\n",avg_tat);
return 0;
}C++ Program
#include<iostream>
using namespace std;
int main()
{
int bt[20],p[20],wt[20],tat[20],pr[20],i,j,n,total=0,pos,temp,avg_wt,avg_tat;
cout<<"Enter Total Number of Process:";
cin>>n;
cout<<"\nEnter Burst Time and Priority\n";
for(i=0;i<n;i++)
{
cout<<"\nP["<<i+1<<"]\n";
cout<<"Burst Time:";
cin>>bt[i];
cout<<"Priority:";
cin>>pr[i];
p[i]=i+1; //contains process number
}
//sorting burst time, priority and process number in ascending order using selection sort
for(i=0;i<n;i++)
{
pos=i;
for(j=i+1;j<n;j++)
{
if(pr[j]<pr[pos])
pos=j;
}
temp=pr[i];
pr[i]=pr[pos];
pr[pos]=temp;
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 is 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=total/n; //average waiting time
total=0;
cout<<"\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];
cout<<"\nP["<<p[i]<<"]\t\t "<<bt[i]<<"\t\t "<<wt[i]<<"\t\t\t"<<tat[i];
}
avg_tat=total/n; //average turnaround time
cout<<"\n\nAverage Waiting Time="<<avg_wt;
cout<<"\nAverage Turnaround Time="<<avg_tat;
return 0;
}Output
