Output:
Constructor of class-simple
Enter values for a and b (sample data 6 and 7)...6 7
The two integers are ...6 7
The sum of the variables 6 + 7 = 13

Whenever an object of a class is declared as a member of another class it is known as a container class. In the container-ship the object of one class is declared in another class.
Illustration: C++ program to illustrate the containership
#include < iostream >
using namespace std;
class outer
{
int date;
public:
void get ( );
};
class inner
{
int value;
outer ot;
//object ot of class outer is declared in
class inner
public;
void getdata( );
};
void outer::get( )
{
cout << "\nEnter a value";
cin >> data;
cout << "\nThe given value is" << data;
}
void inner:: getdata( )
{
cout << "\nEnter a value";
cin >> value;
cout << "\nThe given value is " << value;
ot.get( ); //calling of get( ) of class outer in getdata( )of class inner
}
int main ( )
{
inner in;
in.getdata( );
return( );
}
Output:
Enter a value 10
To given value is 10
 Enter a value 20
The given value is 20

When an object is passed by value the function creates its own copy of the object and works on it. Therefore any changes made to the object inside the function do not affect the original object.
C++ program to illustrate how the pass by value method work.
#include < iostream >
using namespace std;
class Sample
{
private:
int num;
public:
void set(int x)
{
num = x;
}
void pass(Sample obj 1, Sample obj 2)
{
obj 1.num= 100;
obj 2.num=200;
cout << "\n\n Changed value of object1 "<< obj 1.num;
cout << "\n\n Changed value of object1 "<< obj 2.num;
}
void print ( )
{
cout << num;
}
};
int main ( )
{
Sample s1;
Sample s2;
Sample s3;
s1.set(10);
s2.set(20);
cout << "\n\t\tExample program for pass by value \n\n\n";
cout << "\n\n Value of object1 before passing;s1.print( );
cout << "\n\n Value of object2 before passing";
s2.print( );
s3.pass(s1,s2);
cout << "\n\n Value of object1 after passing";
s1.print( );
cout << "\n\n Value of object2 after passing";
s2.print ( );
return ( );
}
Output:
Example program for PASS BY VALUE
Value of object 1before passing 10
Value of object 2 before passing 20
Changed value of object 1 100
Changed value of object 200
Value of object 1 after passing 10
Value of object 1 after passing 20

#include < iostream >
using namespace std
class nest
{
int a;
int square _num( )
{
return a* a;
{
}
public;
void input_ num( )
{
cout << "\nEnter a number";
cin >> a;
}
int cube_num( )
{
retun a* a*a;
void disp_num( )
{
int sq=square_num( ); //nesting of member function
int cu=cube_num( ); //nesting of member function
cout <<"\n The square of" << a << "is" << sq;
cout << "\nThe cube of" << a << "is" << cu;
}
};
int main( )
{
nest n1;
n1.input_ num( );
n1.disp _num( );
return 0;
}
Output:
Enter a number 5
The square of 5 is 25
The cube of 5 is 125

Objects can be created in two methods:
i. Global object,
ii. Local object
(i) Global Object:
If an object is declared outside all the function bodies or by placing their names immediately after the closing brace of the class declaration then it is called as Global object. These objects can be used by any function in the program.
(ii) Local Object:
If an object is declared with in a function then it is called local object. It cannot be accessed from outside the function.