passing reference in c++
// C++ program to swap two numbers using
// pass by reference.
#include <iostream>
using namespace std;
void swap(int& x, int& y)
{
int z = x;
x = y;
y = z;
}
int main()
{
int a = 45, b = 35;
cout << "Before Swap\n";
cout << "a = " << a << " b = " << b << "\n";
swap(a, b);
cout << "After Swap with pass by reference\n";
cout << "a = " << a << " b = " << b << "\n";
}
// C++ program to demonstrate differences between pointer
// and reference.
#include <iostream>
using namespace std;
struct demo
{
int a;
};
int main()
{
int x = 5;
int y = 6;
demo d;
int *p;
p = &x;
p = &y; // 1. Pointer reintialization allowed
int &r = x;
// &r = y; // 1. Compile Error
r = y; // 1. x value becomes 6
p = NULL;
// &r = NULL; // 2. Compile Error
p++; // 3. Points to next memory location
r++; // 3. x values becomes 7
cout << &p << " " << &x << endl; // 4. Different address
cout << &r << " " << &x << endl; // 4. Same address
demo *q = &d;
demo &qq = d;
q->a = 8;
// q.a = 8; // 5. Compile Error
qq.a = 8;
// qq->a = 8; // 5. Compile Error
cout << p << endl; // 6. Prints the address
cout << r << endl; // 6. Print the value of x
return 0;
} 
