PRIORITY CPU Scheduling Algorithm.

Problem No: 03

Name of the problem: PRIORITY CPU Scheduling Algorithm.

Theory:  Priority scheduling is a non-preemptive algorithm and one of the most common scheduling algorithms in batch systems. Each process is assigned a priority. Process with the highest priority is to be executed first and so on.

Code:

#include<bits/stdc++.h>

using namespace std;

main()

{

    int p[20],bt[20],pri[20],tat[20],wt[20],i,k,n;

    float tatavg, wtavg;

    cout<<"enter the number of process: " ;

    cin>>n;

    for(i=0; i<n; i++)

    {

        p[i]=i;

        cout<<"enter the burst time and priority of process ";

        cout<<i<<" :";

        cin>>bt[i]>>pri[i];

        cout<<endl;

    }

    for(i=0; i<n; i++)

    {

        for(k=i+1; k<n; k++)

        {

            if(pri[i]>pri[k])

            {

                swap(p[i],p[k]);

                swap(bt[i],bt[k]);

                swap(pri[i],pri[k]);

            }

        }

    }

    wtavg=wt[0]=0;

    tatavg=tat[0]=bt[0];

    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];

    }

    printf("\nprocess\t\tpriority\tburst time\twaiting time\tturnaround time");

    for(i=0; i<n; i++)

    {

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

    }

    printf("\naverage waiting time  %f",wtavg/n);

    printf("\naverage turnaround time %f",tatavg/n);

}