Library management

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

#define MAX 100

typedef struct {
    int id;
    char title[100];
    char author[100];
    int issued; // 0: available, 1: issued
} Book;

Book books[MAX];
int book_count = 0;

// File operations
void load_books() {
    FILE *fp = fopen("books.dat", "rb");
    if (fp) {
        fread(&book_count, sizeof(int), 1, fp);
        fread(books, sizeof(Book), book_count, fp);
        fclose(fp);
    }
}

void save_books() {
    FILE *fp = fopen("books.dat", "wb");
    fwrite(&book_count, sizeof(int), 1, fp);
    fwrite(books, sizeof(Book), book_count, fp);
    fclose(fp);
}

// Add a book
void add_book() {
    Book b;
    b.id = book_count + 1;
    printf("Title: "); scanf(" %[^\n]", b.title);
    printf("Author: "); scanf(" %[^\n]", b.author);
    b.issued = 0;
    books[book_count++] = b;
    save_books();
    printf("Book added!\n");
}

// Search by title
void search_title() {
    char key[100];
    printf("Enter title to search: "); scanf(" %[^\n]", key);
    for (int i = 0; i < book_count; i++)
        if (strstr(books[i].title, key))
            printf("ID:%d Title:%s Author:%s Issued:%d\n", books[i].id, books[i].title, books[i].author, books[i].issued);
}

// Search by author
void search_author() {
    char key[100];
    printf("Enter author to search: "); scanf(" %[^\n]", key);
    for (int i = 0; i < book_count; i++)
        if (strstr(books[i].author, key))
            printf("ID:%d Title:%s Author:%s Issued:%d\n", books[i].id, books[i].title, books[i].author, books[i].issued);
}

// Sort books (by title)
int cmp_title(const void *a, const void *b) {
    return strcmp(((Book*)a)->title, ((Book*)b)->title);
}
void sort_title() {
    qsort(books, book_count, sizeof(Book), cmp_title);
    printf("Books sorted by title.\n");
}

// Issue/Return
void issue_book() {
    int id; printf("Enter book ID to issue: "); scanf("%d", &id);
    for (int i = 0; i < book_count; i++)
        if (books[i].id == id && books[i].issued == 0) {
            books[i].issued = 1;
            save_books();
            printf("Book issued.\n"); return;
        }
    printf("Book not found or already issued.\n");
}
void return_book() {
    int id; printf("Enter book ID to return: "); scanf("%d", &id);
    for (int i = 0; i < book_count; i++)
        if (books[i].id == id && books[i].issued == 1) {
            books[i].issued = 0;
            save_books();
            printf("Book returned.\n"); return;
        }
    printf("Book not found or not issued.\n");
}

// Display
void display_books() {
    for (int i = 0; i < book_count; i++)
        printf("ID:%d Title:%s Author:%s Issued:%d\n", books[i].id, books[i].title, books[i].author, books[i].issued);
}

// Main menu
int main() {
    load_books();
    int choice;
    do {
        printf("\n1.Add Book 2.Search Title 3.Search Author 4.Sort Title 5.Issue 6.Return 7.Display 0.Exit\n");
        scanf("%d", &choice);
        switch(choice) {
            case 1: add_book(); break;
            case 2: search_title(); break;
            case 3: search_author(); break;
            case 4: sort_title(); break;
            case 5: issue_book(); break;
            case 6: return_book(); break;
            case 7: display_books(); break;
        }
    } while (choice != 0);
    return 0;
}