C++ Pointers

👉 C++ Pointers

A pointer in C++ is a variable that stores the memory address of another variable.
Pointers are essential for dynamic memory, arrays, functions, and low-level programming.

🔹 1. Pointer Declaration

int *ptr;

  • int → type of data it points to

  • * → pointer symbol

  • ptr → pointer variable

🔹 2. Pointer Initialization

int x = 10;
int *ptr = &x;

  • &x → address of x

  • ptr stores that address

🔹 3. Access Value Using Pointer (Dereferencing)

cout << *ptr; // Output: 10

  • ptr → address

  • *ptr → value at that address

🔹 4. Change Value Using Pointer

*ptr = 25;
cout << x; // Output: 25

🔹 5. Pointer and Array Relationship

int arr[3] = {10, 20, 30};
int *p = arr;

cout << *p; // 10
cout << *(p + 1); // 20
cout << *(p + 2); // 30

🔹 6. Pointer Arithmetic

p++; // moves to next element

➡ Pointer moves by sizeof(type) bytes.

🔹 7. Null Pointer

int *p = nullptr;

✔ Safe initialization
✔ Avoids garbage address

🔹 8. Pointer in Functions (Call by Reference)

void change(int *x) {
*x = 50;
}

int a = 10;
change(&a);
cout << a; // 50

🔹 9. Pointer vs Reference

PointerReference
Can be NULLCannot be NULL
Can be reassignedCannot be reassigned
Needs dereferencingNo dereferencing
More flexibleSafer & simpler

🔹 10. Common Pointer Types

Pointer to Pointer

int x = 10;
int *p = &x;
int **pp = &p;

Constant Pointer

int x = 10;
int *const p = &x;

Pointer to Constant

const int x = 10;
const int *p = &x;

❌ Common Mistakes

int *p;
*p = 10; // ❌ uninitialized pointer

✔ Correct:

int x = 10;
int *p = &x;

📌 Summary

  • Pointer stores a memory address

  • & → get address, * → access value

  • Used with arrays, functions, dynamic memory

  • Must be initialized properly

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