------------1.h-------------------
int a;

class test1
{
public:
test1(){a=5;}
};


-------------1.cpp--------------------
#include "1.h"

-------------2.h-----------------------
#include "1.h"

extern int a;

-------------2.cpp--------------------
#include <iostream.h>
#include "2.h"

void main()
{
char d;
test1* newclass=new test1();
cout<<a;
cin>>d;
}