void Doctor::input()
 {
     char t;
     cout<<"主治医生基本信息"<<endl;
     fstream outfile("D:\\aa.txt",ios::out|ios::app);//以写的方式 打开文件
    if(!outfile)
       cout<<"打开文件失败"<<endl;
    else
    {
        cout<<"姓名：";
        cin>>name;
        outfile<<name<<" ";
        cout<<"性别：";
        cin>>sex;
        if(sex=='M'|sex=='m')
           outfile<<"男"<<" ";
        else if(sex=='f'|sex=='F')
           outfile<<"女"<<" ";
         else
         {
             cout<<"请重新输入性别："<<endl;
            cin>>sex;
            if(sex=='M'|sex=='m')
               outfile<<"男"<<" ";
            else if(sex=='f'|sex=='F')
               outfile<<"女"<<" ";
          }
          cout<<"年龄";
          cin>>age;
          outfile<<age<<" ";
          cout<<"诊费";
          cin>>office_vist_fees;
          outfile<<office_vist_fees<<" ";
          cout<<"专业说明";
          cin>>specially;
          outfile<<specially<<" ";
          outfile.close();
    }
    cout<<"是否继续添加医生信息(y|n)"<<endl;
    cin>>t;
    if(t=='y')
        input();
    else
        return ;  
  }

如果是在内存里面增加，删除元素是很容易的。像这样直接写到文件当中就难了。还没有操作过在文件中删除部分内容的方法。只知道所有数据重新写入，覆盖原文件。