## Saturday, December 3, 2011

### Round Robin Process Sheduling Algorithm and Example Source Code in C

Round robin is the most widely used process scheduling algorithm .The basic strategy for round robin scheduling is that if there are n process,each of the process will receive 1/n CPU Execution Time.Each process is allotted a  time quanta, for which its is executed.The incoming processes are kept in a ready list while another one is executing.If the time quanta allotted for a process is over,then that process is moved to ready and the next process in the ready list is executed for the allotted time quanta.The Complete Example Implementation Source Code in C of Round Robin Algorithm to schedule N Processes and to calculate the Execution,wait time and turn around time is given below.
`````` #include<stdio.h>
void main()
{
int n,i,k,x=0,s=0,r=0,q=0,x=0,a,e,t;
float m,p=0;
printf("Enter the number of process:");
scanf("%d",&n);
printf("Enter the execution time:");
for(i=0;i<n;i++)
{
scanf("%d",&a[i]);
e[i]=a[i];
}
printf("Enter the quanta:");
scanf("%d",&q);
printf("After round robin sheduling:");
for(i=0;i<n;i++)
{
if(x<a[i])
{
x=a[i];
}
}
k=x/q;
while(s<=k)
{
for(i=0;i<n;i++)
{
if(a[i]>0)
{
if(a[i]>q)
{
r=r+q;
a[i]=a[i]-q;
printf("P%d\t",i+1);
}
else
{
r=r+a[i];
a[i]=a[i]-q;
printf("P%d ",i+1);
t[i]=r;
}
}
}
s++;
}
printf("\nPROCESS EXECUTION TIME  WAIT TIME  TURN AROUND TIME\n");
for(i=0;i<n;i++)
{
printf(" %d \t\t %d\t\t %d\t\t %d\t\t \n",i,e[i],x,t[i]);
x=x+q;
}
m=x/n;
printf("Average waiting time=%f",m);
printf("Average turn around time=");
for(i=0;i<n;i++)
p=p+t[i];
p=p/n;
printf("%f",p);
}
`````` 