Pointers in Modern C++

A pointer is an object that stores the address of another object or function. Unlike a reference, a pointer is itself a separate object with its own value.

Basic pointer declaration

#include <iostream>
int main() {
    int value{10};
    int* ptr = &value;
    std::cout << value << '\n';
    std::cout << *ptr << '\n';
}

Here:

• &value means “the address of value”,

• ptr stores that address,

• *ptr means “the object pointed to by ptr”.

Address-of and indirection

Two operators are fundamental:

• & gives the address of an object,

• * dereferences a pointer to access the pointed-to object.

int value{7};
int* ptr = &value;
int copy = *ptr;

Changing an object through a pointer

#include <iostream>
int main() {
    int value{10};
    int* ptr = &value;
    *ptr = 99;
    std::cout << value << '\n'; // prints 99
}

Pointers can be reassigned

Unlike references, pointers can be changed to point somewhere else.

#include <iostream>
int main() {
    int a{10};
    int b{20};
    int* ptr = &a;
    std::cout << *ptr << '\n'; // 10
    ptr = &b;
    std::cout << *ptr << '\n'; // 20
}

Pointers can be null

A pointer can intentionally point to nothing.

int* ptr = nullptr;

This is one of the major differences between pointers and references.

Pointers to dynamic objects

Pointers are often associated with dynamic allocation:

int* ptr = new int(42);
delete ptr;

This is valid C++, but Modern C++ strongly discourages using raw owning pointers as a beginner's default style. Later chapters will show why smart pointers are usually better.

Pointers are objects too

A pointer itself has storage, a type, and a value.

int value{5};
int* ptr = &value;

Here:

• value is an int object,

• ptr is an int* object,

• the value stored in ptr is an address.