sp-lab/10.c

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

#define MAX 50


void fcfs(int requests[], int n, int head) {
    int total = 0;

    printf("\n--- FCFS ---\n");
    printf("Order: %d", head);

    for (int i = 0; i < n; i++) {
        total += abs(requests[i] - head);
        head = requests[i];
        printf(" -> %d", head);
    }

    printf("\nTotal Head Movement: %d\n", total);
}

// ── SCAN ──────────────────────────────────────────────────────────────────
void scan(int requests[], int n, int head, int disk_size) {
    int total = 0;
    int req[MAX];

    // copy and sort requests
    for (int i = 0; i < n; i++) req[i] = requests[i];
    for (int i = 0; i < n - 1; i++)
        for (int j = 0; j < n - i - 1; j++)
            if (req[j] > req[j+1]) { int t = req[j]; req[j] = req[j+1]; req[j+1] = t; }

    // find where head sits in sorted array
    int pos = 0;
    while (pos < n && req[pos] < head) pos++;

    printf("\n--- SCAN (moving towards higher tracks first) ---\n");
    printf("Order: %d", head);

    // go right (higher) first
    for (int i = pos; i < n; i++) {
        total += abs(req[i] - head);
        head = req[i];
        printf(" -> %d", head);
    }
    if (head != disk_size - 1) {

        total += abs((disk_size - 1) - head);
        head = disk_size - 1;

        printf(" -> %d", head);
    }

    // go left (lower)
    for (int i = pos - 1; i >= 0; i--) {
        total += abs(req[i] - head);
        head = req[i];
        printf(" -> %d", head);
    }

    printf("\nTotal Head Movement: %d\n", total);
}

// ── MAIN ──────────────────────────────────────────────────────────────────
int main() {
    int requests[MAX], n, head, disk_size;

    printf("Enter number of requests: ");
    scanf("%d", &n);
    printf("Enter requests: ");
    for (int i = 0; i < n; i++)
        scanf("%d", &requests[i]);

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

    printf("Enter disk size: ");
    scanf("%d", &disk_size);

    fcfs(requests, n, head);
    scan(requests, n, head, disk_size);

    return 0;
}