Pointers and References

A pointer holds an address. A reference is another name for an existing object. Both avoid copying, but they behave differently.

Pointers

& takes an address and * reads the value at that address. Always check a pointer before dereferencing it.

int score = 88;
int* pointer = &score;

std::cout << pointer << "\n";  // address
std::cout << *pointer << "\n"; // 88

*pointer = 92;
std::cout << score << "\n";    // 92

References

A reference must be initialised and cannot be reseated. It is the safer default for passing values without copying.

int score = 88;
int& alias = score;

alias = 95;
std::cout << score << "\n"; // 95

Lifetime

Never return a pointer or reference to a local variable. It is destroyed when the function ends, leaving a dangling pointer.

Practice

1. Create a pointer to an int and print both the address and value.
2. Change a value through a reference.
3. Explain why returning a reference to a local variable is unsafe.

Hands-on exercise

Write a function swapValues(int& a, int& b) that swaps two numbers using references.
Call it and print the values before and after.

Recap

Pointers store addresses and can be null. References are aliases and cannot be reseated. Watch object lifetimes.