Memory Address

Memory Address

Every variable lives at a specific location in memory. The address-of operator & placed in front of a variable name asks where that location is.

Getting an address

#include <iostream>
using namespace std;

string food = "Pizza";
cout << &food << endl;

The output is a number: the memory address where food actually lives.

Addresses are hexadecimal

Addresses print in hexadecimal (base 16), using the digits 0 to 9 and the letters A to F, usually with a 0x prefix:

cout << &food << endl;   // 0x7ffe0000a1c

You never do math with that number; it is just a label for a spot in memory.

The address can change

Memory is shared with everything else running on the computer, so the same program can print one address in one run and a different address in another. That is normal.

& has two jobs

• &variable in an expression is the address-of operator: it produces the address.
• & in a declaration - string &meal = food; - marks a reference.

The position tells you which meaning is in play.

TL;DR

• &variable gives the memory address of that variable.
• Addresses print in hexadecimal, often with a 0x prefix.
• The address value differs between runs and machines.
• & on a variable name is the address-of operator; & in a declaration is the reference marker.