pointer.cpp

#include <iostream>
#include <string>
using namespace std;

int main() {

    // ===================================================
    // 1. CREATING POINTERS
    // ===================================================
    // A pointer is a variable that STORES THE MEMORY ADDRESS of another variable as its value.
    // The pointer type must match the data type of the variable it points to.
    
    string food = "Pizza";
    
    // Pointer declaration using `*` and assigning memory address using `&`
    string* ptr = &food; // Preferred way

    /* Other valid syntax options for pointer declaration:
       string *ptr = &food;
       string * ptr = &food;
    */

    cout << "=== 1. CREATING POINTERS ===" << endl;
    cout << "Value of food       : " << food << endl;    // Output: Pizza
    cout << "Memory addr (&food) : " << &food << endl;   // Output: 0x...
    cout << "Pointer value (ptr) : " << ptr << endl;     // Output: 0x... (Same as &food)


    // ===================================================
    // 2. DEREFERENCING OPERATOR (*)
    // ===================================================
    // Using `*ptr` OUTSIDE of declaration is called the DEREFERENCE OPERATOR.
    // Purpose: Gets the ACTUAL VALUE stored at the memory address held by the pointer.

    cout << "\n=== 2. DEREFERENCING POINTER ===" << endl;
    cout << "Address via ptr     : " << ptr << endl;     // Displays Memory Address
    cout << "Value via *ptr      : " << *ptr << endl;    // Dereference -> Displays "Pizza"


    // ===================================================
    // 3. MODIFYING POINTER VALUE
    // ===================================================
    // Changing `*ptr` will modify the original variable's value (`food`) in memory.

    cout << "\n=== 3. MODIFYING POINTER VALUE ===" << endl;
    *ptr = "Hamburger"; // Modifies the value at memory location via pointer

    cout << "New value via *ptr  : " << *ptr << endl;    // Output: Hamburger
    cout << "New value of food   : " << food << endl;    // Output: Hamburger


    // ===================================================
    // KEY TAKEAWAYS & ASTERISK (*) RULES:
    // ===================================================
    /*
     1. Asterisk `*` during DECLARATION (string* ptr) -> Creates a pointer variable.
     2. Asterisk `*` during EXECUTION (*ptr)          -> Dereference operator (Accesses/modifies the value).
     3. Ampersand `&`                                 -> Address-of operator (Retrieves memory address).
    */

    return 0;
}