how can i access the members of parent object?...

ex.

class Cparent
{
public:
int a;
void funtionX();
}

class Cchild
{
public:
void funtionY();
}


void Cparent::functionX()
{
a=0;
Cchild chd;
chd.functionY();
}

void Cchild::functionY()
{
// how can i access "a" from HERE without parse any data
}

NOTE 1: the code may contain errors, but i only want the method for access
NOTE 2: the two classes are separated in two files .cpp files.