用c语言写一个图书信息管理系统要求首界面有登录，注册，退出的功能，登录成功后界面有录入图书信息，查找图书信息，修改图书信息，分类统计图书数量的功能

好的，我可以帮您解决这个问题。首先，您需要使用C语言编写一个控制台应用程序，该程序将实现您所述的功能。下面是一个简单的实现：

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

struct book {
    char title[100];
    char author[100];
    char publisher[100];
    int year;
    int copies;
};

struct user {
    char username[100];
    char password[100];
};

int main() {
    int choice;
    printf("Welcome to the Book Management System!\n");
    printf("1. Login\n");
    printf("2. Register\n");
    printf("3. Quit\n");
    printf("Enter your choice: ");
    scanf("%d", &choice);

    if (choice == 1) {
        // Login
        struct user users[100];
        int num_users = 0;
        FILE *fp = fopen("users.dat", "rb");
        if (fp != NULL) {
            fread(&num_users, sizeof(int), 1, fp);
            fread(users, sizeof(struct user), num_users, fp);
            fclose(fp);
        }

        char username[100], password[100];
        printf("Enter your username: ");
        scanf("%s", username);
        printf("Enter your password: ");
        scanf("%s", password);

        int i;
        for (i = 0; i < num_users; i++) {
            if (strcmp(users[i].username, username) == 0 &&
                strcmp(users[i].password, password) == 0) {
                printf("Login successful!\n");
                break;
            }
        }

        if (i == num_users) {
            printf("Invalid username/password!\n");
            exit(1);
        }

        // Main menu
        printf("1. Add book\n");
        printf("2. Find book\n");
        printf("3. Update book\n");
        printf("4. Statistics\n");
        printf("5. Logout\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);

        struct book books[100];
        int num_books = 0;
        fp = fopen("books.dat", "rb");
        if (fp != NULL) {
            fread(&num_books, sizeof(int), 1, fp);
            fread(books, sizeof(struct book), num_books, fp);
            fclose(fp);
        }

        while (choice != 5) {
            switch (choice) {
                case 1: {
                    // Add book
                    printf("Enter title: ");
                    scanf("%s", books[num_books].title);
                    printf("Enter author: ");
                    scanf("%s", books[num_books].author);
                    printf("Enter publisher: ");
                    scanf("%s", books[num_books].publisher);
                    printf("Enter year: ");
                    scanf("%d", &books[num_books].year);
                    printf("Enter copies: ");
                    scanf("%d", &books[num_books].copies);
                    num_books++;

                    fp = fopen("books.dat", "wb");
                    fwrite(&num_books, sizeof(int), 1, fp);
                    fwrite(books, sizeof(struct book), num_books, fp);
                    fclose(fp);
                    break;
                }
                case 2: {
                    // Find book
                    char title[100];
                    printf("Enter title: ");
                    scanf("%s", title);

                    int i;
                    for (i = 0; i < num_books; i++) {
                        if (strcmp(books[i].title, title) == 0) {
                            printf("Title: %s\n", books[i].title);
                            printf("Author: %s\n", books[i].author);
                            printf("Publisher: %s\n", books[i].publisher);
                            printf("Year: %d\n", books[i].year);
                            printf("Copies: %d\n", books[i].copies);
                            break;
                        }
                    }

                    if (i == num_books) {
                        printf("Book not found!\n");
                    }
                    break;
                }
                case 3: {
                    // Update book
                    char title[100];
                    printf("Enter title: ");
                    scanf("%s", title);

                    int i;
                    for (i = 0; i < num_books; i++) {
                        if (strcmp(books[i].title, title) == 0) {
                            printf("Enter new title: ");
                            scanf("%s", books[i].title);
                            printf("Enter new author: ");
                            scanf("%s", books[i].author);
                            printf("Enter new publisher: ");
                            scanf("%s", books[i].publisher);
                            printf("Enter new year: ");
                            scanf("%d", &books[i].year);
                            printf("Enter new copies: ");
                            scanf("%d", &books[i].copies);
                            break;
                        }
                    }

                    if (i == num_books) {
                        printf("Book not found!\n");
                    } else {
                        fp = fopen("books.dat", "wb");
                        fwrite(&num_books, sizeof(int), 1, fp);
                        fwrite(books, sizeof(struct book), num_books, fp);
                        fclose(fp);
                    }
                    break;
                }
                case 4: {
                    // Statistics
                    int num_copies = 0;
                    int year_counts[100] = {0};

                    int i;
                    for (i = 0; i < num_books; i++) {
                        num_copies += books[i].copies;
                        year_counts[books[i].year]++;
                    }

                    printf("Total number of copies: %d\n", num_copies);
                    printf("Number of books per year:\n");
                    for (i = 0; i < 100; i++) {
                        if (year_counts[i] > 0) {
                            printf("%d: %d\n", i, year_counts[i]);
                        }
                    }
                    break;
                }
                default: {
                    printf("Invalid choice!\n");
                    break;
                }
            }

            // Main menu
            printf("1. Add book\n");
            printf("2. Find book\n");
            printf("3. Update book\n");
            printf("4. Statistics\n");
            printf("5. Logout\n");
            printf("Enter your choice: ");
            scanf("%d", &choice);
        }

        printf("Logout successful!\n");
    } else if (choice == 2) {
        // Register
        struct user users[100];
        int num_users = 0;
        FILE *fp = fopen("users.dat", "rb");
        if (fp != NULL) {
            fread(&num_users, sizeof(int), 1, fp);
            fread(users, sizeof(struct user), num_users, fp);
            fclose(fp);
        }

        char username[100], password[100];
        printf("Enter your username: ");
        scanf("%s", username);

        int i;
        for (i = 0; i < num_users; i++) {
            if (strcmp(users[i].username, username) == 0) {
                printf("Username already exists!\n");
                exit(1);
            }
        }

        printf("Enter your password: ");
        scanf("%s", password);

        strcpy(users[num_users].username, username);
        strcpy(users[num_users].password, password);
        num_users++;

        fp = fopen("users.dat", "wb");
        fwrite(&num_users, sizeof(int), 1, fp);
        fwrite(users, sizeof(struct user), num_users, fp);
        fclose(fp);

        printf("Registration successful!\n");
    } else if (choice == 3) {
        // Quit
        printf("Goodbye!\n");
        exit(0);
    } else {
        printf("Invalid choice!\n");
        exit(1);
    }

    return 0;
}

该程序使用了结构体来表示图书和用户信息，并将它们保存在二进制文件中。用户可以登录、注册、退出，登录成功后可以添加、查找、更新图书信息，以及进行分类统计。如果您需要对该程序进行进一步修改和扩展，可以根据您的需求进行改动。