What is a reference?

Learn that a reference is an alias for a variable.

What is a reference?

A reference is an alias for an existing variable. Once a reference is declared, every operation through it affects the original variable, because both refer to the same memory location.

Example: int x = 10; int& r = x;. Here r is an alias for x. Writing r = 20; also makes x become 20. Unlike a pointer, a reference cannot be re-bound to another variable after its first binding; it is fixed at initialization.

Reference versus pointer

A reference is like a pointer but safer. A pointer is a separate variable and can be nullptr; a reference is bound to a variable at initialization and cannot be null.

The syntax is also cleaner: you write r, not *p. But a reference is less flexible; it cannot be re-bound. So when you want 'an alias for a variable', choose a reference; when you want 'an independent address', choose a pointer.

Exercise Modify through a reference

Declare int x = 10;. Bind a reference with int& r = x;. Write r = 20;. Finally print x with std::cout.

Show example solution

#include <iostream>

int main() {
    int x = 10;
    int& r = x;
    r = 20;
    std::cout << x << "\n";
    return 0;
}

Test yourself

What is a reference?
- A memory address
- A kind of pointer
- A new variable type
- An alias for a variable
Show answer

An alias for a variable — A reference is an alias for an existing variable.

Reference declaration

int x = 10;
int____ r = x;

Show answer

int x = 10;
int& r = x;

Match each expression to its meaning

int& r

Reference declaration
int x = 10

Variable declaration
r = 20

Reference assignment
std::cout << x

Print

Next lesson: Declaring references

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