C++在线图书出售系统

#include <iostream>
#include <fstream>
#include <string>
#include <conio.h> 
using namespace std;
class book
{
public:
void Bookinformation();
private:
char booknumber,booktion[80];
 };
void book::Bookinformation()
{ifstream in("图书信息.txt");
 cout<<"请输入您购买的图书编号:";
 cin>>booknumber;
   while(in)
   {in.getline(booktion,80);
      if (booktion[0]==booknumber)
  {cout<<booktion<<endl;
   in.close();
   return;
  }
   }
 cout<<"无此图书，请重新输入图书编号"<<endl;
 Bookinformation();
}
class buyer
{
public: