Reference Operator

Description

Using references in C++ is technique of acquiring memory location (address) from specific data types. A reference to a variable can be declared by using &(ampersend) operator. We can use reference like this:

    // Declaring int variable with value of 10
    int var = 10;
    // Declaring reference to integer variable var
    int& ref = var;
    // Printing value of var:
    std::cout<<var<<std::endl;
    // incrementing ref by 10:
    ref += 10;
    // printing reference value:
    std::cout<<ref<<std::endl;
    // Again printing var value:
    std::cout<<var<<std::endl;
    /* OUTPUT:
        10
        20
        20
    */

In this example of usage of references we can see that reference are closely tied to given variable. When declare a reference to specific data in C++, we are inheriting all related data for that specific varible. So, besides the basic value of that data, we are inheriting information about memory location of that specific value. Having that in mind, when we perfom any data manipulation of our created refence, we are affecting our initial variable. Explanation of that behaviour comes from a fact that reference is just a representation of a variable upon which we declared our reference.
In specific point of view, we can imagine references as primitive pointers, because they also carry information about data memory location. Besides that, reference is also a operator, which can be used for operation of referencing. Referencing data in C++ states that we are requesting memory location of wanted data.

int var = 10;
// we are requesting value of variable var:
std::cout<<var<<std::endl;
// 10
// we are requesting memory address of variable var:
std::cout<<&var<<std::endl;
// e.g. => 0x7ffe318d531c

Some of the typical deficiencies of references in compare with pointers are:

1. When reference is created it cannot be re - initialized

2. References cannot be initialized to NULL value, which is often used to indicate that pointers aren't showing to any memory location

3. A reference must be initialized with valid data - meaning that they are only declared when they have valid memory address to reference

Besides these facts, references are much more efficient for usage in C++, because they are preventing memory leakage, they are safer from a point of memory management and they are easier to use.
Reference are popular as input and return values in functions. With this technique, we are preventing copying of our data from one part of program to another and we are certain that any changes in a function will affect our original data.