Сортировка массива структур по одному полю

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

#define LIMIT 5
#define TITLE_BUFFER 80
#define AUTHOR_BUFFER 64

enum points { TITLE, AUTHOR, YEAR };

typedef struct Book {
    char title[TITLE_BUFFER];
    char author[AUTHOR_BUFFER];
    int year;
} BOOK;
typedef BOOK* PBOOK;

void user(enum points);
BOOK input();
void fill(PBOOK);
void print(BOOK);
void show(PBOOK);
int compare(const void*, const void*);

int main() {
    BOOK book[LIMIT];
    fill(book);
    system("cls");
    show(book);
    qsort(book, LIMIT, sizeof(BOOK), compare);
    show(book);
    fflush(stdin);
    getchar();
    return 0;
}

int compare(const void* a, const void* b) {
    PBOOK pa = a;
    PBOOK pb = b;
    return strcmp(pa->author, pb->author);
}

void fill(PBOOK pbook) {
    int i;
    for (i = 0; i < LIMIT; ++i) pbook[i] = input();
}

BOOK input() {
    BOOK book;
    user(TITLE);
    gets_s(book.title, TITLE_BUFFER);
    user(YEAR);
    scanf_s("%i", &book.year);
    fflush(stdin);
    user(AUTHOR);
    gets_s(book.author, AUTHOR_BUFFER);
    return book;
}

void show(PBOOK pbook) {
    int i;
    for (i = 0; i < LIMIT; ++i) print(pbook[i]);
    printf("\n");
}

void print(BOOK book) {
    printf(" %s, %s, %d", book.author, book.title, book.year);
    printf("\n");
}

void user(enum points point) {
    setlocale(LC_CTYPE, ".1251");
    switch (point) {
        case TITLE: printf(" Введите название книги: "); break;
        case AUTHOR: printf(" Введите автора: "); break;
        case YEAR: printf(" Введите год издания: "); break;
    }
    setlocale(LC_CTYPE, ".866");
}