程序代码：

# include <stdio.h>
# include <windows.h>
# include <stdlib.h>
# include <string.h>
struct book
{
    int book_number;
    char book_name[30];
    float book_price;
    char book_class[20];
    int book_sign;
}school_book[30];
void InformationSearch();
void BackStage();
bool Login();
void Initialize();
void AddItem();
void ChangeItem();
void DeletItem();
void ScanItem();
void ChangePassword();
void save(FILE * fp, int i);
void main()//主函数登陆
{
    printf("--------请输入登陆状态-------\n");
    printf("1.游客登录\n");
    printf("2.管理员登陆\n");

    int i;
    scanf("%d", &i);
    switch(i)
    {
    case 1:
        {
            system("cls");
            Sleep(800);
            InformationSearch();break;
        }
    case 2:
        {
            system("cls");
            Sleep(800);
            BackStage();break;
        }
    }
}
void InformationSearch()//信息查询系统
{
    FILE * fp;
    int siz, j, count = 0, i = 0;
    char ch;
    if((fp=fopen("Data", "rb+"))==NULL)
    {
        printf("打开数据文件Data错误！\n");
        exit(0);
    }
    printf(">>>>>>>>>>>>>>欢迎使用图书信息查询系统<<<<<<<<<<<<<<<\n");
    printf("编号   名称   价格（元）  类别\n");
    for(i=0;i<30;i++)
    {
        fread(&school_book[i], sizeof(struct book), 1, fp);
        if(school_book[i].book_number==0)
        {
            break;
        }
        printf("%2d%8s%9.2f%9s", school_book[i].book_number, school_book[i].book_name, school_book[i].book_price, school_book[i].book_class);
        printf("\n");
    }
}
void BackStage()//后台系统
{
    if(Login())
    {
        return;
    }
    while(1)
    {
        printf("--------欢迎登陆图书后台管理系统--------\n");
        printf("1.初始化 所有信息\n");
        printf("2.添加 图书信息\n");
        printf("3.修改 图书信息\n");
        printf("4.删除 图书信息\n");
        printf("5.查看 图书信息\n");
        printf("6.管理员密码修改\n");

        int i;
        scanf("%d", &i);
        switch(i)
        {
        case 1:
            {
                system("cls");
                Sleep(800);
                Initialize();
                break;
            }
        case 2:
            {
                system("cls");
                Sleep(800);
                AddItem();
                break;
            }
        case 3:
            {
                system("cls");
                Sleep(800);
                ChangeItem();
                break;
            }
        case 4:
            {
                system("cls");
                Sleep(800);
                DeletItem();
                break;
            }
        case 5:
            {
                system("cls");
                Sleep(800);
                ScanItem();
                break;
            }
        case 6:
            {
                system("cls");
                Sleep(800);
                ChangePassword();
                break;
            }
        }
    }
}
bool Login()//打开保存密码的文件，并验证
{
    FILE * fp;
    int count;
    char filename[] = "password";
    char stringIn[10];
    char stringOut[10];

//    if((fp=fopen(filename, "rb+"))==NULL)
//    {
//        printf("这是您首次使用本系统\n默认密码为admin\n");
//        fp=fopen(filename, "wb+");
//        fprintf(fp, "admin");
//        fclose(fp);
//    }
    while ((fp = fopen(filename, "rb+")) == NULL)
     {
         printf("这是您首次使用本系统\n默认密码为admin\n");
         fp = fopen(filename, "wb+") ;
         fprintf(fp, "admin");
         fclose(fp);
     }
    fscanf(fp, "%s", stringOut);
    printf("请输入密码： ");
    scanf("%s", stringIn);
    count = strcmp(stringIn, stringOut);
    if(count==0)
        return false;
    else
        return true;
}
void Initialize()
{
    char ch;
    int i = 0;
    FILE * fp;
    fp = fopen("Data", "wb+");
    do
    {
        printf("=================================\n");
        printf("请输入第%d项图书信息\n", i+1);
        printf("图书编号： ");
        scanf("%d", &school_book[i].book_number);
        ch = getchar();
        printf("图书名称： ");
        scanf("%s", school_book[i].book_name);
        ch = getchar();
        printf("图书价格： ");
        scanf("%f", &school_book[i].book_price);
        ch = getchar();
        printf("图书类别： ");
        scanf("%s", school_book[i].book_class);
        ch = getchar();
        school_book[i].book_sign = 1;
        printf("=================================\n");
        ++i;
        printf("是否继续录入？（Y/N）");
        ch = getchar();
    }while(ch=='y'&&'Y');
    save(fp, i);
    fclose(fp);
}
void AddItem()
{
    char ch;
    int i, j = 0;
    FILE * fp;
    if((fp = fopen("Data", "rb+"))==NULL)
    {
        printf("cannot open file!\n");
        return;
    }

    for(i=0;i<30;i++)
    {
        fread(&school_book[i], sizeof(struct book), 1, fp);
        if(school_book[i].book_number==0)
        {
            break;
        }
    }
    fclose(fp);
    j = i;
    do
    {
        printf("=================================\n");
        printf("请输入第%d项图书信息\n", i+1);
        printf("图书编号： ");
        scanf("%d", &school_book[i].book_number);
        ch = getchar();
        printf("图书名称： ");
        scanf("%s", school_book[i].book_name);
        ch = getchar();
        printf("图书价格： ");
        scanf("%f", &school_book[i].book_price);
        ch = getchar();
        printf("图书类别： ");
        scanf("%s", school_book[i].book_class);
        ch = getchar();
        school_book[i].book_sign = 1;
        printf("=================================\n");
   
        printf("是否继续录入？（Y/N）");
        ch = getchar();
        ++i;
    }while(ch=='y'&&'Y');
    if((fp = fopen("Data", "ab+"))==NULL)
    {
        printf("cannot open file!\n");
        return;
    }
    for(;j<i;j++)
    {
        if(fwrite(&school_book[j], sizeof(struct book), 1, fp)!=1)
        {
            printf("Error!\n");
            break;
        }
    }

    fclose(fp);
}
void ChangeItem()
{
   
    FILE * fp;
    int siz, h, j, i = 0;
    char ch;
    if((fp=fopen("Data", "rb+"))==NULL)
    {
        printf("打开数据文件Data错误！\n");
        exit(0);
    }
    printf("编号   名称   价格（元）  类别\n");
    for(i=0;i<30;i++)
    {
        fread(&school_book[i], sizeof(struct book), 1, fp);
        if(school_book[i].book_number==0)
        {
            break;
        }
        printf("%2d%8s%9.2f%9s", school_book[i].book_number, school_book[i].book_name, school_book[i].book_price, school_book[i].book_class);
        printf("\n");
    }
    fclose(fp);
    printf(">>>>>>>>>>>>>>>>>>>>>>>>>>>>\n");
    printf(">>>>>>>>>>>>>>>>>>>>>>>>>>>>\n");
    printf("请输入要修改的记录序号：  ");
    scanf("%d", &j);
    fp = fopen("Data", "wb+");

    for(h=0;h<=i;h++)
    {
        if(school_book[h].book_number==j)
        {
            printf("=================================\n");
            printf("请输入第%d项图书信息\n", j);
            printf("图书编号： ");
            scanf("%d", &school_book[h].book_number);
            ch = getchar();
            printf("图书名称： ");
            scanf("%s", school_book[h].book_name);
            ch = getchar();
            printf("图书价格： ");
            scanf("%f", &school_book[h].book_price);
            ch = getchar();
            printf("图书类别： ");
            scanf("%s", school_book[h].book_class);
            ch = getchar();
            school_book[h].book_sign = 1;
            printf("=================================\n");
        }
        if(fwrite(&school_book[h], sizeof(struct book), 1, fp)!=1)
        {
            printf("Error!");
            break;
        }
    }
    save(fp, i);
    fclose(fp);
}
void DeletItem()
{

    FILE * fp;
    int siz, h, j, i = 0;
    char ch;
    if((fp=fopen("Data", "rb+"))==NULL)
    {
        printf("打开数据文件Data错误！\n");
        exit(0);
    }
    printf("编号   名称   价格（元）  类别\n");
    for(i=0;i<30;i++)
    {
        fread(&school_book[i], sizeof(struct book), 1, fp);
        if(school_book[i].book_number==0)
        {
            break;
        }
        printf("%2d%8s%9.2f%9s", school_book[i].book_number, school_book[i].book_name, school_book[i].book_price, school_book[i].book_class);
        printf("\n");
    }
    fclose(fp);
    printf(">>>>>>>>>>>>>>>>>>>>>>>>>>>>\n");
    printf(">>>>>>>>>>>>>>>>>>>>>>>>>>>>\n");
    printf("请输入要删除的记录序号：  ");
    scanf("%d", &j);
    fp = fopen("Data", "wb+");

    for(h=0;h<=i;h++)
    {
        if(school_book[h].book_number==j)
        {
            continue;
        }
        if(fwrite(&school_book[h], sizeof(struct book), 1, fp)!=1)
        {
            printf("Error!");
            break;
        }
    }
    save(fp, i);
    fclose(fp);
}
void ScanItem()
{
    FILE * fp;
    int siz, j, count = 0, i = 0;
    char ch;
    if((fp=fopen("Data", "rb+"))==NULL)
    {
        printf("打开数据文件Data错误！\n");
        exit(0);
    }
    printf("编号   名称   价格（元）  类别\n");
    for(i=0;i<30;i++)
    {
        fread(&school_book[i], sizeof(struct book), 1, fp);
        if(school_book[i].book_number==0)
        {
            break;
        }
        printf("%2d%8s%9.2f%9s", school_book[i].book_number, school_book[i].book_name, school_book[i].book_price, school_book[i].book_class);
        printf("\n");
    }

}
void ChangePassword()
{
    FILE * fp;
    int count;
    char filename[] = "password";
    char ch[10];
    char stringIn[10];
    char stringOut[10];

    fp = fopen(filename, "rb+");

    fscanf(fp, "%s", stringOut);
    printf("请输入旧密码： ");
    scanf("%s", stringIn);
    count = strcmp(stringIn, stringOut);
    if(count==0)
    {
        printf("密码验证成功\n新密码： ");
        scanf("%s", ch);
        fp = fopen(filename, "wb+") ;
        fprintf(fp, ch);
        fclose(fp);
    }
    else
    {
        printf("密码验证失败\n");
        return;
    }
}
void save(FILE * fp, int i)
{
//    fprintf(fp, "%d%10s%6.2f%10s", book[i].book_number, book[i].book_name, book[i].book_price, book[i].book_class);
//    fprintf(fp, "\n");
    int j;
    for(j=0;j<=i;j++)
    {
        if(fwrite(&school_book[j], sizeof(struct book), 1, fp)!=1)
        {
            printf("error!");
            break;
        }
    }
}