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C++ reference

Provides ways to directly manipulate memory. It bring many used cases such as dynamic memory allocation and advanced data structures.

Reference

In c++, a reference variable is an alias to an existing variable. It is declared with an ampersand & between the reference type and the variable name.

It is primary use in function parameter.
It allow function to modify the value of the variable referenced.

int exam_grad = 85;
int& score = exam_grade;

Note: this notation is correct too int &score = exam_grade;

The score variable is an alias to exam_grade variable.
When the value of score is changed, the value of exam_grade change in the same way.

 Be careful of two things when declaring reference variable:

• References must be initialized
• References cannot be reassigned

Pass-by-reference

Reference can be initialized in function parameter. Allowing easy manipulation of the original variable.

void add_five(int& i) {
   i += 5; 
}

//In main
int a = 100;
add_five(a);

// a = 105

Memory address

When not used in a declaration, the ampersand & is called the adress of operator and is used to access the memory address of a variable.

int exam_grad = 85;
std::cout << &exam_grade;