C++ :: How To Make Class Globally Accessible

I have a class like this:

file one :

Code:
class X : public Y {
public:
virtual int query(int, int);
// constructor
X(int, int);

[Code] .....

And i construct my M and Nby calling :

Code:
X Y(a,b); and afterwords by calling

Code:
result = Y (c,d) i get my result.

The problem is I need to be able to call result = Y (c,d) from outside my main function and get results but i don't know how to do this. So I want to be able to do something like this.

Code:
#include <iostream>
int g;
void func2(int *h){
*h = g;

[Code] .....