C++代码可以运行，但是保存不了文件，怎么解决？谢谢！！！

修改完善如下，供参考：

#include <stdio.h>
#include <string>
/*定义医生结构体*/
struct Doctor
{
     char ID[50];       //医生编号
     char Name[50];     //姓名
     char Keshi[11];     //科室
     char Room[11];     //诊室
};
/*声明医生数组及医生数量*/
struct Doctor Doctors[100];
int num=0;
/*通过医生编号返回数组下标*/
int Doctor_SearchByIndex(char id[])
{
    int i;
    for (i=0;i<num;i++)
    {
        if (strcmp(Doctors[i].ID,id)==0)
        {
            return i;
        }
    }
    return -1;
}
/*通过姓名返回数组下标*/
int Doctor_SearchByName(char name[])
{
    int i;
    for (i=0;i<num;i++)
    {
        if (strcmp(Doctors[i].Name,name)==0)
        {
            return i;
        }
    }  
    return -1;  
}  
/*显示单条医生记录*/  
void Doctor_DisplaySingle(int index)
{
    printf("%10s%10s%10s%8s\n","医生编号","姓名","科室","诊室");  
    printf("-------------------------------------------------------------\n");  
    printf("%10s%10s%10s%8s\n",Doctors[index].ID,Doctors[index].Name,Doctors[index].Keshi,
                                                                     Doctors[index].Room);
}  
/****1、增加医生记录*****/
void Doctor_Insert()
{  
    while(1)  
    {
        printf("请输入医生编号:");
                                        //scanf("%s",&Doctors[index].Room);
        fflush(stdout);rewind(stdin);
        scanf("%s",Doctors[num].ID);    //scanf("%s",&Doctors[num].ID);
                                        //getchar();
        printf("请输入姓名:");
        fflush(stdout);rewind(stdin);
        scanf("%s",Doctors[num].Name);//scanf("%s",&Doctors[num].Name);
                                       //getchar();
        printf("请输入科室:");
        fflush(stdout);rewind(stdin);
        scanf("%s",Doctors[num].Keshi);//scanf("%s",&Doctors[num].Keshi);
                                       //getchar();
        printf("请输入诊室:");
        fflush(stdout);rewind(stdin);
        scanf("%s",Doctors[num].Room);//scanf("%s",&Doctors[num].Room);
                                      //getchar();
        num++;
        printf("是否继续?(Y/N)，继续请按任意键，否则输入N:");
        fflush(stdout);rewind(stdin);
        if ((getchar())=='N')
        {  
            break;
        }
     }  
}
/******2、修改医生信息**********/  
void Doctor_Modify()  
{  
    while(1) 
    {  
        char id[50];
        int index; 
        printf("请输入要修改的医生的医生编号:");
        scanf("%s",id);  //scanf("%s",&id);
        getchar();  
        index=Doctor_SearchByIndex(id);
        if (index==-1)
        {  
            printf("该医生不存在!\n"); 
         }
        else  
        {  
            printf("你要修改的医生信息为:\n");
            Doctor_DisplaySingle(index);
            printf("-- 请输入新值--\n"); 
            printf("请输入医生编号:");
            fflush(stdout);rewind(stdin);
            scanf("%s",Doctors[index].ID);  //scanf("%s",&Doctors[index].ID);
                                            //getchar();
            printf("请输入姓名:");
            fflush(stdout);rewind(stdin);
            scanf("%s",Doctors[index].Name);//scanf("%s",&Doctors[index].Name);
                                            //getchar();
            printf("请输入科室:");
            fflush(stdout);rewind(stdin);
            scanf("%s",Doctors[index].Keshi);//scanf("%s",&Doctors[index].Keshi);
                                            //getchar();
            printf("请输入诊室:");
            fflush(stdout);rewind(stdin);
            scanf("%s",Doctors[index].Room);//scanf("%s",&Doctors[index].Room);
                                           //getchar();
         }
         printf("是否继续?(Y/N)，继续请按任意键，否则输入N:");
         fflush(stdout);rewind(stdin);
         if ((getchar())=='N')
         {
            break;
         }
     }
} 
/****3、删除医生信息****/  
void Doctor_Delete()  
{
    int i;  
    while(1)  
    {  
        char id[50];  
        int index;  
        printf("请输入要删除的医生的医生编号:");
        fflush(stdout);rewind(stdin);
        scanf("%s",id);                 // scanf("%s",&id);
                                        //getchar();
        index=Doctor_SearchByIndex(id);
        if (index==-1)  
        {
            printf("医生不存在!\n");  
        }  
        else  
        {  
            printf("你要删除的医生信息为:\n"); 
            Doctor_DisplaySingle(index);
            printf("是否真的要删除?(Y/N)");  
            if ((getchar())=='Y')
            {  
                for (i=index;i<num-1;i++)  
                {  
                    Doctors[i]=Doctors[i+1];//把后边的对象都向前移动
                } 
                num--;  
             }  
            getchar();
            printf("已删除\n");
         }
         printf("是否继续删除?(Y/N)，继续请按任意键，否则输入N:");
         fflush(stdout);rewind(stdin);
         if ((getchar())=='N')
         {  
            break;
         }
     }  
}  
 
/****4、按姓名查询******/  
void Doctor_Select()  
{
    while(1)  
    {  
        char name[50];  
        int index;  
        printf("请输入要查询的医生的姓名:");
        fflush(stdout);rewind(stdin);
        scanf("%s",name); //scanf("%s",&name);
                          //getchar();
        index=Doctor_SearchByName(name);
        if (index==-1) 
        {  
            printf("医生不存在!\n");
        } 
        else  
        {  
            printf("你要查询的医生信息为:\n"); 
            Doctor_DisplaySingle(index);  
        }
        printf("是否继续?(Y/N)，继续请按任意键，否则输入N:");
        fflush(stdout);rewind(stdin);
        if ((getchar())=='N')
        {  
            break;
        }
     }
}  
 
 
/*显示医生信息*/  
void Doctor_Display()
{  
    int i;  
    printf("%10s%10s%10s%8s\n","医生编号","姓名","科室","诊室");  
    printf("-------------------------------------------------------------\n");  
    for (i=0;i<num;i++)  
    {
        printf("%10s%10s%10s%8f\n",Doctors[i].ID,Doctors[i].Name,Doctors[i].Keshi,
                                                                 Doctors[i].Room);
    }  
}  
/*将医生信息从文件（Database.txt）中读出*/  
void IO_ReadInfo()
{ 
    FILE *fp;  
    int i;  
    if ((fp=fopen("Database.txt","rb"))==NULL)  
    {  
        printf("不能打开文件!\n");
        return;  
    }
    if (fread(&num,sizeof(int),1,fp)!=1)  
    {  
        num=-1;  
    }
    else  
    {  
        for(i=0;i<num;i++)  
        {  
            fread(&Doctors[i],sizeof(struct Doctor),1,fp);  
        }
    } 
    fclose(fp);  
} 
/*将医生信息写入文件（Database.txt）*/  
void IO_WriteInfo()
{
    FILE *fp; 
    int i;  
    if ((fp=fopen("Database.txt","wb"))==NULL)  
    {  
        printf("不能打开文件!\n");  
        return;
    }  
    if (fwrite(&num,sizeof(int),1,fp)!=1)
    {  
        printf("写入文件错误!\n");  
    }  
    for (i=0;i<num;i++)
    {  
        if (fwrite(&Doctors[i],sizeof(struct Doctor),1,fp)!=1)  
        {  
            printf("写入文件错误!\n");  
        }  
    }
    fclose(fp);  
} 
/***********主程序*********/ 
void main()  
{ 
    int choice;
    IO_ReadInfo();          //读取文件
    while(1)  
    {  
        /*主菜单*/  
        printf("\n------ 医生预约系统------\n");  
        printf("1. 增加医生记录\n");
        printf("2. 修改医生记录\n");  
        printf("3. 删除医生记录\n");  
        printf("4. 按姓名查询医生记录\n");  
        printf("5. 按诊室排序\n");  
        printf("6. 保存并退出\n");  
        printf("请选择(1-6):");
        scanf("%d",&choice);  
        getchar();  
        switch(choice)  
        { 
        case 1:  
            Doctor_Insert();
            break; 
        case 2: 
            Doctor_Modify(); 
            break;  
        case 3:  
            Doctor_Delete();
            break;  
        case 4:  
            Doctor_Select();
            break;  
        case 5:  
            break;
        case 6:
            IO_WriteInfo();
            exit(0);
            //break;
        }
    }
}