Question:

What is meant by reference variable in C++?

Answer:

In C++, reference variable allows you create an alias (second name) for an already existing variable. A reference variable can be used to access (read/write) the original data. That means, both the variable and reference variable are attached to same memory location. In effect, if you change the value of a variable using reference variable, both will get changed (because both are attached to same memory location).

How to create a reference variable in C++
Appending an ampersand (&) to the end of datatype makes a variable eligible to use as reference variable.

int a = 20;
int& b = a;

The first statement initializes a an integer variable a. Second statement creates an integer reference initialized to variable a 
Take a look at the below example to see how reference variables work.

int main ()
{
	int   a;
	int&  b = a;
 
	a = 10;
	cout << "Value of a : " << a << endl;
	cout << "Value of a reference (b) : " << b  << endl;
 
	b = 20;
	cout << "Value of a : " << a << endl;
	cout << "Value of a reference (b) : " << b  << endl;
 
	return 0;
}

Above code creates following output.

Value of a : 10
Value of a reference (b) : 10
Value of a : 20
Value of a reference (b) : 20


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