2c_C-SCAN.c

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

void cscan(int Ar[20], int n, int start);
void sort(int Ar[20], int n);

int range, lastLocation;
int main() {

    int diskQueue[20], n, start, i, max;
    printf("Enter the range :");
    scanf("%d", &range);

    printf("Enter the size of Queue: ");
    scanf("%d", &n);

    printf("Enter the Queue: ");
    for(i=1;i<=n;i++) {                                     /* head element to be read */ 
        scanf("%d",&diskQueue[i]);
    }

    printf("Enter the initial head position: ");
    scanf("%d", &start);                                

    diskQueue[0] = start;                                    /* injecting to the first position */
    ++n;

    sort(diskQueue, n);                                     /* total of n+1 elements */    
    cscan(diskQueue, n, start);

    return 0;

}

void cscan(int Ar[20], int n, int start) {

    int i, pos, diff, seekTime=0, current;
    // position of the disk to start seeking 
    for(i=0;i<n;i++) {                                      

        if(Ar[i]==start) {
            pos=i;
            break;
        }

    }
    // start seeking to the right
    printf("\nMovement of Cylinders\n");
    for(i=pos;i<n-1;i++) {

        diff = abs(Ar[i+1] - Ar[i]);
        seekTime+= diff;
        printf("Move from %d to %d with seek time %d\n", Ar[i], Ar[i+1], diff);

    }
    current=i;               /* last element position */                  
    //moving to end location
    lastLocation = range -1;
    printf("Move from %d to %d with seek time %d\n", Ar[i], lastLocation,(lastLocation-Ar[i]));
    seekTime+=lastLocation-Ar[i];
    Ar[i]= lastLocation;
    current=0;                                                                      /* start and end are same as circular, so start state i.e, 0*/

    // last element to 0, the first element

    printf("Move from %d to %d with seek time %d\n", Ar[i], current, 0);            /* head movement as cylinders are treated as a circular list (C-SCAN always goes back to the first track) */
    seekTime += lastLocation;
    // start seeking to the right from 0

    for(i=0;i<pos;i++) {

        diff = abs(Ar[i] - current);
        seekTime+= diff;
        printf("Move from %d to %d with seek time %d\n", current, Ar[i], diff);
        current = Ar[i];

    }

    printf("\nTotal Seek Time: %d", seekTime);

    printf("\n");

}

void sort(int Ar[20], int n) {

    int i, j, tmp;

    for(i=0;i<n-1;i++) {

        for(j=0;j<n-1-i;j++) {

            if(Ar[j]>Ar[j+1]) {

                tmp = Ar[j];
                Ar[j] = Ar[j+1];
                Ar[j+1] = tmp;

            }

        }

    }

}

/*
OUTPUT
Enter the range :200
Enter the size of Queue: 8
Enter the Queue: 98 183 41 122 14 124 65 67
Enter the initial head position: 53

Movement of Cylinders
Move from 53 to 65 with seek time 12
Move from 65 to 67 with seek time 2
Move from 67 to 98 with seek time 31
Move from 98 to 122 with seek time 24
Move from 122 to 124 with seek time 2
Move from 124 to 183 with seek time 59
Move from 183 to 199 with seek time 16
Move from 199 to 0 with seek time 0
Move from 0 to 14 with seek time 14
Move from 14 to 41 with seek time 27

Total Seek Time: 386
*/