Please find and correct the error in my c++ program. "Linker Error: Undefined symbol _main in module c0.ASM"
The program is for transfering content of one file to another.

#include<fstream.h>
#include<iostream.h>
#include<conio.h>
class student
{
int rollno;
char name[20];
int tm;
public:
void input();
void transfer();
void output();
}
obj;
void student::input()
{
char ch='y';
ofstream outf;
outf.open("mark.dat");
while(ch=='y')
{
cout<<"Enter rollno, name and mark";
cin>>rollno>>name>>tm;
outf.write((char*)&obj,sizeof(obj));
cout<<"wish to enter more(Y/N)";
cin>>ch;
}
outf.close();
}
void student::transfer()
{
ofstream outf;
ifstream inf;
inf.open("mark.dat");
inf.open("trans.dat");
while(inf)
{
inf.read((char*)&obj,sizeof(obj));
outf.write((char*)&obj,sizeof(obj));
}
outf.close();
inf.close();
}
void student::output()
{
ifstream inf;
inf.open("trans.dat");
while(inf)
{
inf.read((char*)&obj,sizeof(obj));
cout<<"Rollno"<<rollno;
cout<<"Name"<<name;
cout<<"Total"<<tm;
}
getch();
inf.close();
}

The error i get is
compiling 10.cpp
linking ...\OUTPUT\10.EXE
.Linker Error: Undefined symbol _main in module c0.ASM

I think the error is due to the missing of void main. But i don't know where i should put it.