Differences between pointers & references from C++ perspective.

pointers_and_references.cpp

#include <iostream>

using namespace std;

int main() {
	/*
	 * References are often confused with pointers but three major
	 * differences between references and pointers are:
	 * - You cannot have NULL references. You must always be able to assume
	 * that a reference is connected to a legitimate piece of storage.
	 * - Once a reference is initialized to an object, it cannot be
	 * changed to refer to another object. Pointers can be pointed to
	 * another object at any time.
	 * - A reference must be initialized when it is created. Pointers can
	 * be initialized at any time.
	 * */

	int x(0);
	int y(1);

	// A reference refers to the same memory address, so it shares
	// the same memory address, but not holds like a pointer and not
	// creates a new one.
	int &alpha = x;
	// A pointer is a variable that holds a memory address where a value lives.
	int *beta = &y;
	// "Regular" variables (not pointers), they have memory address too, but not holds them.
	int default_behavior = x;

	cout << "Address of x " << &alpha << " is the same like of alpha " << &x << endl;
	cout << "Address of y " << &y << " isn't the same like of beta " << &beta << endl;
	cout << endl;
	cout << "Value of x is " << x << " and value of alpha is " << alpha << endl;
	cout << "Value of y is " << y << " and value of beta is " << beta << endl;
	cout << "#########################################################################" << endl;
	cout << "Default behavior address " << &default_behavior << " and value " << default_behavior << endl;
	cout << "#########################################################################" << endl;

	// Assignment of a new value to the alpha variable sets this value as
	// well to x. As far as they share the same memory space, we can access
	// this value without any syntax sugar.
	alpha = 10; // reference

	// Assignment of a new value to the beta pointer sets this value only
	// to y. As far as beta holds the only memory address to get/assign a 
	// value we need to use syntax sugar *.
	*beta = 20;  // pointer


	cout << "Values and memory addresses after reassignment." << endl;
	cout << endl;
	cout << "Address of x " << &alpha << " is the same like of alpha " << &x << endl;
	cout << "Address of y " << &y << " isn't the same like of beta " << &beta << endl;
	cout << endl;
	cout << "Value of x is " << x << " and value of alpha is " << alpha << endl;
	cout << "Value of y is " << y << " and value of beta is " << beta << endl;
	cout << endl;
	// Eventually we see changes only in ints values but not in memory addresses.

	return 0;
}