A nested class is a class which is declared in another enclosing class. A nested class is a member and as such has the same access rights as any other member. The members of an enclosing class have no special access to members of a nested class; the usual access rules shall be obeyed.

For example, program 1 compiles without any error and program 2 fails in compilation.

Program 1

#include<iostream>

using namespace std;

/* start of Enclosing class declaration */
class Enclosing {
private:
int x;

/* start of Nested class declaration */
class Nested {
int y;
void NestedFun(Enclosing *e) {
cout<<e->x; // works fine: nested class can access
// private members of Enclosing class
}
}; // declaration Nested class ends here
}; // declaration Enclosing class ends here

int main()
{

}

Program 2

#include<iostream>

using namespace std;

/* start of Enclosing class declaration */
class Enclosing {

int x;

/* start of Nested class declaration */
class Nested {
int y;
}; // declaration Nested class ends here

void EnclosingFun(Nested *n) {
cout<<n->y; // Compiler Error: y is private in Nested
}
}; // declaration Enclosing class ends here

int main()
{

}