在用c语言编写登录系统时，怎么实现如果输入用户名和密码时发现输入错误后，能使用退格键删除的功能。拜托大家帮忙看看。谢谢！

//这是和登陆部分有关的代码，麻烦大家看看吧！
void login() /*登录*/
{
    void menu();
    system("cls");
    if(flag)
    {
        printf("  已经登录!\n");
        printf("Press any key to continue…\n");
        getchar();
        getchar();
        system("cls");
        menu();
    }
    int load();
    int n,i,m,w;
    FILE *fp;
    if((fp=fopen("D:\\file.txt","rb"))!=NULL) /*不是空文件*/
      n=load(); /*打开文件*/
    else
      n=0;
    struct student s;
    char password[20];
    int d,q;
    printf("\n\t请选择登录身份：1.管理员      2.用户     [ ]\b\b");
    scanf("%d",&d);
    if(d==1)
    {
        printf("\n\t\t\t请输入密码：");
        getchar();
        int j=0;
        while(1)      
        {
            password[j]=getch();
            if(password[j]=='\r')
              break;
            printf("*");
            j++;
        }
        password[j]='\0';
        if(!strcmp(password,"930322")) /*判断密码是否正确*/
        {
            flag=1;
            printf("\n\t登录成功!\n");
            printf("\tPress [ Enter ] key to continue…");
            getchar();
            system("cls");
            menu();
        }
        if(!flag)
        {
           printf("\t\n密码错误!\n");
           printf("What do you want to do next? 1.继续登录  2.返回菜单   [ ]\b\b");
           scanf("%d",&q);
           if(q==1) /*继续登录*/
           {
               system("cls");
               login();
           }
           else if(q==2) /*返回主菜单*/
           {
               system("cls");
               menu();
           }
        }
    }
    else
    {
       printf("\n\t\t\t用户名:");
       scanf("%s",s.name);
       printf("\t\t\t密码:");
       int j=0;
       while(1)
        {
            password[j]=getch();
            if(password[j]=='\r')
              break;
            printf("*");
            j++;
        }
       password[j]='\0';
       flag=0; /*未登录时flag=0*/
       for(i=0;i<n;i++)
         if(!strcmp(s.name,stu[i].name)&&!strcmp(s.name,password))
         {
           flag=1; /*登录成功flag=1*/
           break;
         }
      if(flag)
      {
         printf("\n\t登录成功!\n");
         printf("\tPress any key to continue…\n");
         getchar(); getchar();
         system("cls");
         menu(); /*登录成功后返回主菜单*/
      }
      else
      {
        m=0; /*设置m是为了避免陷入 登录失败时 跳不出登录界面*/
        w=1; /*设置w是为了避免输出多次 “用户不存在”*/
        int q; /*q为选项*/
        do
        {
            if(w>0)
               printf("用户名不存在或密码错误!\n"); /*第一次登录时输入不存在的用户时显示*/
            printf("What do you want to do next? 1.继续登录  2.返回菜单   [ ]\b\b");
            scanf("%d",&q);
            if(q==1) /*继续登录*/
            {
                login();
                m=1;
            }
            else if(q==2) /*返回主菜单*/
            {
                system("cls");
                menu();
                m=1;
            }
            else
            {
                printf("选择错误!请重新选择:\n");
                w=0;
            }
        }while(m==0);
      }
    }
}