When we declare a pointer variable like so, its content is not intialized:

int* ptr;

In other words, it contains an address of “somewhere”, which is of course not a valid location. This is dangerous! We need to initialize a pointer by assigning it a valid address.

But suppose we don’t know where we are pointing to, we can use a null pointer.

nullptr is a new keyword introduced in C++11. It provides a typesafe pointer value representing an empty pointer.

We can use nullptr like so:

int* ptr = nullptr;

Note: In older C/C++ code, NULL was used for this purpose. nullptr is meant as a modern replacement to NULL.