What are the consequences of attempting to access data via a null pointer?

Accessing data through a null pointer (nullptr in C++ or NULL in C) leads to undefined behavior of the program. In practice, this usually causes a crash with a segmentation fault or a memory access error, as address 0 typically does not belong to the process and does not contain valid data.

Example:

int* p = nullptr;
int value = *p; // Error: dereferencing a null pointer

This behavior should be avoided by always checking the pointer before use.