C++ Fundamentals for Professionals/

...

/

Null Pointer

Null Pointer

This lesson highlights the key features of the null pointer.

We'll cover the following...

Before C++11, 0 was often used to represent an empty or null value when the NULL macro was not applicable. The issue with the literal 0 is that it can be the null pointer (void*)0 or the number 0. This is defined by the context.

Therefore, a small program with the number 0 should be confusing.

C++
#include <iostream>
#include <typeinfo>
int main(){
  std::cout << std::endl;
  int a= 0;
  int* b= 0;
  auto c= 0;
  std::cout << typeid(c).name() << std::endl;
  auto res= a+b+c;
  std::cout << "res: " << res << std::endl;
  std::cout << typeid(res).name() << std::endl;
}

The variable c is of type int, and the variable res is of type pointer to int: int*. Pretty simple, right? The expression a+b+c in line ...