UNIT IV: Pointers

Introduction:

"This topic is often considered challenging, but it's also what gives C++ so much of its power and flexibility. Think of it this way: every variable you create is stored somewhere in your computer's memory, and each memory location has a unique address, just like every house on a street has a unique address.

A pointer is simply a special variable that doesn't store a value like 10 or 'A'; instead, it stores a memory address. By using pointers, we can work directly with memory locations, which allows for highly efficient programming, dynamic memory allocation, and the creation of complex data structures like linked lists. Let's break it down step-by-step."

1. Addresses and Pointers: The Basics

Concept:

• The Address-Of Operator (&): This unary operator gives you the memory address of a variable.
• Pointer Variable: A variable designed to hold a memory address. You declare a pointer by putting an asterisk (*) between the data type and the variable name. The data type tells the pointer what kind of variable it is expected to point to.

Syntax:

      data_type *pointer_name; // Declaration
pointer_name = &variable_name; // Initialization

Example Program 1: Declaring a Pointer and Getting an Address

#include <iostream>
using namespace std;

int main() {
    int score = 95; // A regular integer variable.
    int* scorePtr;  // A pointer that can hold the address of an integer.

    // Use the address-of operator (&) to get the memory address of 'score'.
    scorePtr = &score;

    cout << "Value of the 'score' variable: " << score << endl;
    cout << "Memory address of 'score' variable (using &): " << &score << endl;
    
    cout << "\\nValue of the 'scorePtr' pointer: " << scorePtr << endl;
    cout << "The pointer now holds the address of the 'score' variable." << endl;
    
    return 0;
}

A syntax quibble: Where to put the star? All of these are the same to the compiler: int* ptr; int *ptr; int * ptr;

The first one (int* ptr) is often preferred as it emphasizes the type is "pointer to int".

Expected Output (the address will be different on your machine):