MIT-Curricular/OS/C/Week11/qq1.c

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

void sstf(int requests[], int n, int head) {
    int total_seek = 0;
    int completed = 0;
    int visited[100] = {0};
    int current = head;

    printf("\nSSTF Disk Scheduling\n");
    printf("Seek Sequence: %d", head);

    while (completed < n) {
        int min_distance = INT_MAX;
        int min_index = -1;

        for (int i = 0; i < n; i++) {
            if (!visited[i]) {
                int distance = abs(requests[i] - current);
                if (distance < min_distance) {
                    min_distance = distance;
                    min_index = i;
                }
            }
        }

        visited[min_index] = 1;
        current = requests[min_index];
        total_seek += min_distance;
        completed++;
        printf(" -> %d", current);
    }

    printf("\nTotal Seek Time: %d\n", total_seek);
}

void scan(int requests[], int n, int head, int disk_size) {
    int total_seek = 0;
    int direction = 1; // 1 for moving right, 0 for moving left
    int current = head;

    printf("\nSCAN Disk Scheduling\n");
    printf("Seek Sequence: %d", head);

    // Sort requests
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n - i - 1; j++) {
            if (requests[j] > requests[j + 1]) {
                int temp = requests[j];
                requests[j] = requests[j + 1];
                requests[j + 1] = temp;
            }
        }
    }

    // Find position of head in sorted array
    int index;
    for (index = 0; index < n; index++) {
        if (requests[index] >= head)
            break;
    }

    // Move right
    for (int i = index; i < n; i++) {
        current = requests[i];
        printf(" -> %d", current);
        total_seek += abs(current - head);
        head = current;
    }

    // Move to the end of disk
    printf(" -> %d", disk_size - 1);
    total_seek += abs(disk_size - 1 - head);
    head = disk_size - 1;

    // Move left
    for (int i = index - 1; i >= 0; i--) {
        current = requests[i];
        printf(" -> %d", current);
        total_seek += abs(current - head);
        head = current;
    }

    printf("\nTotal Seek Time: %d\n", total_seek);
}

void cscan(int requests[], int n, int head, int disk_size) {
    int total_seek = 0;
    int current = head;

    printf("\nC-SCAN Disk Scheduling\n");
    printf("Seek Sequence: %d", head);

    // Sort requests
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n - i - 1; j++) {
            if (requests[j] > requests[j + 1]) {
                int temp = requests[j];
                requests[j] = requests[j + 1];
                requests[j + 1] = temp;
            }
        }
    }

    // Find position of head in sorted array
    int index;
    for (index = 0; index < n; index++) {
        if (requests[index] >= head)
            break;
    }

    // Move right
    for (int i = index; i < n; i++) {
        current = requests[i];
        printf(" -> %d", current);
        total_seek += abs(current - head);
        head = current;
    }

    // Move to the end of disk
    printf(" -> %d", disk_size - 1);
    total_seek += abs(disk_size - 1 - head);

    // Move to the beginning
    printf(" -> 0");
    total_seek += disk_size - 1;
    head = 0;

    // Move right again
    for (int i = 0; i < index; i++) {
        current = requests[i];
        printf(" -> %d", current);
        total_seek += abs(current - head);
        head = current;
    }

    printf("\nTotal Seek Time: %d\n", total_seek);
}

void clook(int requests[], int n, int head) {
    int total_seek = 0;
    int current = head;

    printf("\nC-LOOK Disk Scheduling\n");
    printf("Seek Sequence: %d", head);

    // Sort requests
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n - i - 1; j++) {
            if (requests[j] > requests[j + 1]) {
                int temp = requests[j];
                requests[j] = requests[j + 1];
                requests[j + 1] = temp;
            }
        }
    }

    // Find position of head in sorted array
    int index;
    for (index = 0; index < n; index++) {
        if (requests[index] >= head)
            break;
    }

    // Move right
    for (int i = index; i < n; i++) {
        current = requests[i];
        printf(" -> %d", current);
        total_seek += abs(current - head);
        head = current;
    }

    // Move to first request
    for (int i = 0; i < index; i++) {
        current = requests[i];
        printf(" -> %d", current);
        total_seek += abs(current - head);
        head = current;
    }

    printf("\nTotal Seek Time: %d\n", total_seek);
}

int main() {
    int requests[100], n, head, disk_size, choice;

    printf("Enter the number of disk requests: ");
    scanf("%d", &n);

    printf("Enter the disk requests: ");
    for (int i = 0; i < n; i++) {
        scanf("%d", &requests[i]);
    }

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

    printf("Enter the disk size (0 to size-1): ");
    scanf("%d", &disk_size);

    do {
        printf("\n\nDisk Scheduling Algorithms\n");
        printf("1. SSTF (Shortest Seek Time First)\n");
        printf("2. SCAN\n");
        printf("3. C-SCAN\n");
        printf("4. C-LOOK\n");
        printf("5. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                sstf(requests, n, head);
                break;
            case 2:
                scan(requests, n, head, disk_size);
                break;
            case 3:
                cscan(requests, n, head, disk_size);
                break;
            case 4:
                clook(requests, n, head);
                break;
            case 5:
                printf("Exiting program...\n");
                break;
            default:
                printf("Invalid choice!\n");
        }
    } while (choice != 5);

    return 0;
}