What is a reference variable?

A reference is defined as an alias for another variable. In short, it is like giving a different name to a pre-existing variable. Once a reference is initialized to the variable, we can use either the reference name or the variable to refer to that variable.

Creating references in C++

The basic syntax to create a reference is -

Data type& new variable = previous variable

The newly created variable will now refer to the previous variable.

For example -

int i = 17 // The variable i is declared as 17

Creating the reference of i will be as -

int& x = i // Here x will be called as the integer variable initialised to r

C++ code

#include <iostream>
 
using namespace std;
 
int main () {
   int    i; // Declare variable I as int
   double d; // Declare variable d as double type
 
   // declare reference variables for I and d
   int&    r = i;// r is reference to i
   double& s = d;// s is reference to d 
   
   i = 5;
   cout << "Value of i : " << i << endl;
   cout << "Value of i reference : " << r  << endl;
 
   d = 11.7;
   cout << "Value of d : " << d << endl;
   cout << "Value of d reference : " << s  << endl;
   
   return 0;
}

Output

Difference between Reference and Pointers

References	Pointers
We cannot have a NULL reference.	The concept of NULL pointers is allowed.
A reference assigned to a particular object cant be changed.	Pointers, on the other hand, can point to different objects at any time.
A reference is also initialized at the time of its creation.	Pointers can be initialized at any time.

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