throw de;

#include <fstream>
#include <memory>
#include <iostream>
using namespace std;  
class error
{
protected:
 fstream errfile;
public:
 void printmsg(char *msg);
 void logmsg(char *msg);
};
void error::printmsg(char *msg)
{
 cout << msg;
}
void error::logmsg(char *msg)
{
 errfile.open("error.log",ios::app);
 errfile << msg;
}
class fileerror:public error
   {
   };
   class divisionbyzero:public error
   {
   }

#include "error.h"
#include <iostream>
using namespace std;
fileerror fe;
divisionbyzero de;
int main()
{
     fstream f;
     float dividend, divisor,quotient;
try
{
 cout << "Enter a number " << endl;
     cin >> dividend;
     cout << "Enter another number " << endl;
     cin >> divisor;
     // if the divisor is zero we should
     // get the divisionbyzero
     if(divisor==0)
     throw de;
     quotient = dividend/divisor;
     cout << quotient;
     // if there is no file then we should get
     // the fileerror
     f.open("somefile.txt",ios::in);
     if(!f)
     throw fe;
}
catch(divisionbyzero d)
{
d.printmsg("Division by zero \n");
}
catch(fileerror f)
{
f.printmsg("File not found error \n");
}
catch(...)
{
cout<< "Unknown error! \n";
}
     return 0;
   }

throw expression ;