CPU Scheduling Algorithm - Round Robin(C)

This is a C program which implements one of the CPU Scheduling algorithm called Round Robin(RR). Round robin algorithm is mainly used in time sharing systems , it is also similar to First Come First Served(FCFS) algorithm but FCFS does not have that time slicing switch. All the jobs gets executed in this scheduling algorithm , so the advantage here is , its Starvation free.

Download Code

PROGRAM :

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int bt_c[10],bt[10],i,j,n,m[50],r,q,e=0;
    float f,avg=0;
    printf("\nEnter how many jobs ?\t");
    scanf("%d",&n);
    for(i=1; i<=n; i++)
    {
        printf("Enter burst time for job %d :\t",i);
        scanf("%d",&bt[i]);
        bt_c[i]=bt[i]; //stores job has how much burst  time in array  i
    }
    printf("\nEnter Quantum (time slice value) :\t");
    scanf("%d",&q);
    int max=0;
    max=bt[1];
    for(j=1; j<=n; j++)
        if(max<=bt[j])
            max=bt[j];

    if((max%q)==0)
        r=(max/q);
    else
        r=(max/q)+1;
    for(i=1; i<=r; i++)
    {
        printf("\n\nRound %d",i);
        for(j=1; j<=n; j++)
        {
            if(bt[j]>0)
            {
                bt[j]=bt[j]-q;

                if(bt[j]<=0)
                {
                    bt[j]=0;
                    printf("\njob %d is completed",j);
                }
                else
                    printf("\njob %d remaining time is %d",j,bt[j]);
            }
        }

    }
    for(i=1; i<=n; i++)
    {
        e=0;
        for(j=1; j<=r; j++)
        {
            if(bt_c[i]!=0)
            {
                if(bt_c[i]>=q)
                {
                    m[i+e]=q;
                    bt_c[i]-=q;
                }
                else
                {
                    m[i+e]=bt_c[i];
                    bt_c[i]=0;
                }
            }
            else
                m[i+e]=0;
            e=e+n;
        }
    }
    for(i=2; i<=n; i++)
        for(j=1; j<=i-1; j++)
            avg=avg+m[j];
    for(i=n+1; i<=r*n; i++)
    {
        if(m[i]!=0)
        {
            for(j=i-(n-1); j<=i-1; j++)
                avg=m[j]+avg;
        }
    }
    f=avg/n;
    printf("\n\n\nTOTAL WATING TIME:%f\t",avg);
    printf("\n\nAVERAGE WAITING TIME:%f\t\n",f);
    return 0;
}

Download Code

OUTPUT : 

C Program - CPU Scheduling Algorithm : Round Robin