LOOK disk scheduling
Program to implement LOOK disk scheduling algorithm
/* Variable description : req[] - array for taking the request, lower[]-array to store and sort elements lower than current position, upper[]- array to store and sort requests higher than current position of head,temp-temporary variable to help in sorting, a[]- array to store final order of processing requests, mov - to calculate total head movement */
#include<math.h>
#include<stdio.h>
int main()
{
int i,n,j=0,k=0,x=0,l,req[50],mov=0,cp,ub,end, lower[50],upper[50], temp,a[50];
printf("enter the current position\n");
scanf("%d",&cp);
printf("enter the number of requests\n");
scanf("%d",&n);
printf("enter the request order\n");
for(i=0;i<n;i++)
{
scanf("%d",&req[i]);
}
printf("Enter the upper bound\n");
scanf("%d",&ub);
/*break the request array into two arrays : one with requests lower than current and other with requests higher than current position. Also sort these two new arrays*/
for(i=0;i<n;i++)
{
if(req[i]<cp)
{
lower[j]=req[i];
j++;
}
if(req[i]>cp)
{
upper[k]=req[i];
k++;
}
}
//sort the lower array in reverse order
for(i=0;i<j;i++)
{
for(l=0;l<j-1;l++)
{
if(lower[l]<lower[l+1])
{
temp=lower[l];
lower[l]=lower[l+1];
lower[l+1]=temp;
}
}
}
// sort the upper array in ascending order
for(i=0;i<=k;i++)
{
for(l=0;l<k-1;l++)
{
if(upper[l]>upper[l+1])
{
temp=upper[l];
upper[l]=upper[l+1];
upper[l+1]=temp;
}
}
}
printf("Enter the end to which the head is moving (0 - for lower end(zero) and 1 - for upper end\n");
scanf("%d",&end);
switch(end)
{
case 0:
for(i=0;i<j;i++)
{
a[x]=lower[i];
x++;
}
for(i=0;i<k;i++)
{
a[x]=upper[i];
x++;
}
break;
case 1:
for(i=0;i<k;i++)
{
a[x]=upper[i];
x++;
}
for(i=0;i<j;i++)
{
a[x]=lower[i];
x++;
}
break;
}
mov=mov+abs(cp-a[0]);
printf("%d -> %d",cp,a[0]);
for(i=1;i<x;i++)
{
mov=mov+abs(a[i]-a[i-1]);
printf(" -> %d",a[i]);
}
printf("\n");
printf("total head movement = %d\n",mov);
}
