program to represent pass by value concept

c++program code for representing  pass by value concept,also connected with class object concept
#include<iostream.h>
#include<conio.h>
class sample
{
int x;
public:
void read()
{
cout<<"Enter the value\n";
cin>>x;
}
void display()
{
cout<<"The sum is\n";
cout<<x;
}
void add(sample s1,sample s2)
{
x=s1.x+s2.x;
}
};
void main()
{
sample s1,s2,s3;
clrscr();
s1.read();
s2.read();
s3.add(s1,s2);
s3.display();
getch();
}