Write an OS program to implement SCAN Disk Scheduling algorithm.

 #include<stdio.h>

#include<stdlib.h>

int main()

{

      int RQ[100],i,j,n,TotalHeadMoment=0,initial,size,move;

     

      printf("Enter the number of requests: ");

      scanf("%d",&n);

     

      printf("Enter the request sequence: ");

      for(i=0;i<n;i++)

        scanf("%d",&RQ[i]);

     

      printf("Enter initial head position: ");

      scanf("%d",&initial);

     

      printf("Enter total disk size: ");

      scanf("%d",&size);

     

      printf("Enter the head movement direction for high 1 and for low 0: ");

      scanf("%d",&move);

     

      for (i=0;i<n;i++)

      {

          for (j=0;j<n-i-1;j++)

          {

              if (RQ[j]>RQ[j+1])

              {

                 int temp;

                 temp=RQ[j];

                 RQ[j]=RQ[j+1];

                 RQ[j+1]=temp;

              }

          }

      }

     

      int index;

      for (i=0;i<n;i++)

      {

          if (initial<RQ[i])

          {

             index=i;

             break;

          }

      }

     

      if (move==1)

      {

          for (i=index;i<n;i++)

          {

               printf("Serving Request: %d\n",RQ[i]);

               TotalHeadMoment=TotalHeadMoment+abs(RQ[i]-initial);

               initial=RQ[i];

          }

         

          TotalHeadMoment=TotalHeadMoment+abs(size-RQ[i-1]-1);

          initial=size-1;  

          for (i=index-1;i>=0;i--)

          {

              printf("Serving Request: %d\n",RQ[i]);

              TotalHeadMoment=TotalHeadMoment+abs(RQ[i]-initial);

              initial=RQ[i];

          }

      }

     

      else

      {

          for (i=index-1;i>=0;i--)

          {

               printf("Serving Request: %d\n",RQ[i]);

               TotalHeadMoment=TotalHeadMoment+abs(RQ[i]-initial);

               initial=RQ[i];

          }

       

          TotalHeadMoment=TotalHeadMoment+abs(RQ[i+1]-0);

          initial=0;

          for (i=index;i<n;i++)

          {

              printf("Serving Request: %d\n",RQ[i]);

              TotalHeadMoment=TotalHeadMoment+abs(RQ[i]-initial);

              initial=RQ[i];

          }

      }

     

      printf("Total head movement is %d",TotalHeadMoment);

      return 0;

}    

                         

       

/*

           OUTPUT

Enter the number of requests: 8

Enter the request sequence: 98    

183

41

122

14

124

65

67

Enter initial head position: 53

Enter total disk size: 200

Enter the head movement direction for high 1 and for low 0: 1

Serving Request: 65

Serving Request: 67

Serving Request: 98

Serving Request: 122

Serving Request: 124

Serving Request: 183

Serving Request: 41

Serving Request: 14

Total head movement is 331      

*/