FCFS Disk Scheduling algorithm

//I) Consider a disk queue with requests for I/O to blocks on cylinders 98, 183, 41, 122, 14, 124, 65, 67. The head is initially at cylinder number 53 moving towards larger cylinder numbers on its servicing pass. The cylinders are numbered from 0 to 199.

//Write an OS program to implement FCFS Disk Scheduling algorithm to calculate the total head movement (in number of cylinders).

//Solution:

#include<stdio.h>

int front,rear;

void init()

{

front=rear=-1;

}

void display(int *Q)

{

int i;

for(i=front;i<=rear;i++)

printf("\t%d",Q[i]);

}

void enqueu(int *Q,int n,int var)

{

if(rear==n)

printf("\nQueue is Full");

else

{

if(front==-1)

front++;

rear++;

Q[rear]=var;

}

}

int FCFS(int *Q, int n)

{

    int j,seek=0,diff;

    for(j=0;j<n;j++)

    {

        diff=abs(Q[j+1]-Q[j]);

        seek+=diff;

    printf("Disk head moves from %d to %d with seek %d\n",Q[j],Q[j+1],diff);

    }

    return seek;

}

int main()

{

    int queue[20],n,var,head,i,j,k,seek,max;

    float avg;

    init();

   // printf("\nFront=%d\nRear=%d",front,rear);

    printf("\nEnter the max range of disk\n");

    scanf("%d",&max);

    printf("Enter the size of queue request\n");

    scanf("%d",&n);

    printf("Enter the initial head position\n");

    scanf("%d",&head);

    printf("Enter the queue of disk positions to be read\n");

    enqueu(queue,n,head);

    for(i=1;i<=n;i++)

    {

        scanf("%d",&var);

        if(var<0||var>max)

            printf("\nError..!Given Position is invalid\n");

        else

        {

            enqueu(queue,n,var);

        }

    }

    printf("\nGiven Queue is\n");

    display(queue);

    printf("\n\nFCFS Algorithm\n");

    seek=FCFS(queue,n);

    printf("Total seek time is %d\n",seek);

    avg=seek/(float)n;

    printf("Average seek time is %f\n",avg);

    return 0;

}