Unresolved external. Borland ругается - C++ - Ответ 4107286

#include <iostream>
#include <fstream>
#include <cstring>
using namespace std;
 
//---------------------------------------------------------------------------
 
class Name
{
 private:
  static fstream f1;
  string s1;
  string s2;
  int num;
 public:
  Name()
  {}
  static openFile ( )
  {
   f1.open("dat.txt", ios::in | ios::out | ios::binary );
  }
  void setPos ( )
  {
   f1.seekg(0);
   f1.seekp(0);
  }
  void writeData()
  {
   char ans = 'y';
   while( ans == 'y' )
   {
    cout << "\nEnter employer's name: ";
    cin >> s1;
    cout << "\nEnter employer's surname: ";
    cin >> s2;
    cout << "\nEnter employer's number: ";
    cin >> num;
    f1.write(reinterpret_cast<char*>(&(*this)),sizeof(*this));
    cerr << "\nContinue?(Y/N): ";
    cin >> ans;
   }
  }
 
  void readData( )
  {
 
   f1.read(reinterpret_cast<char*>(&(*this)), sizeof(*this));
   cout << "\n Employer's name: " << s1;
   cout << "\n Employer's surname: " << s2;
   cout << "\n Employer's number: " << num << endl;
  }
};
 
//---------------------------------------------------------------------------
int main(int argc, char* argv[])
{
  Name obj;
 
  obj.openFile();
  obj.writeData();
  obj.setPos();
  obj.readData();
 
   system("PAUSE");
 
        return 0;
}