What Is a Pointer?

In C++, a pointer is a variable that stores a memory address. Every variable in your program occupies some location in memory, and a pointer simply holds that address.

Declaring and Using Pointers

int x = 42;        // x lives at some address, say 0x7ffd42
int* ptr = &x;     // ptr stores the address of x (&x)
std::cout << *ptr; // prints 42 (* dereferences the pointer)

• &x — the address-of operator, returns the memory address of x
• *ptr — the dereference operator, reads the value at the address stored in ptr
• int* ptr — declares ptr as a pointer to an int

Pointer Arithmetic

Pointers support arithmetic. Adding 1 to a pointer moves it by sizeof(int) bytes (usually 4):

int arr[] = {10, 20, 30};
int* p = arr;        // points to arr[0]
std::cout << *p;     // 10
p++;                // now points to arr[1]
std::cout << *p;    // 20

This is exactly how array indexing works under the hood: arr[i] is equivalent to *(arr + i).

Null Pointers

A null pointer points to nothing — it's the pointer equivalent of zero:

int* p = nullptr;  // C++11 and later
if (p != nullptr) {
    // safe to dereference
}

Never dereference a null or uninitialized pointer — it causes undefined behavior (usually a segfault).