Null pointer

  • The pointer variable points to a space in memory numbered 0
  • Purpose: Initialize pointer variables
  • Note: memory to which a null pointer points is not accessible

Example 1: null pointer

#include <iostream>
using namespace std;

int main(a)
{
	/ / null pointer
	//1. A null pointer is used to initialize a pointer variable
	int *p = NULL;

	//2. Null Pointers are not accessible
	// Memory numbers between 0 and 255 are occupied by the system and therefore cannot be accessed
	//*p = 100; error

    return 0;
}
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Wild pointer

Pointer variables point to illegal memory space

Example 2: Wild pointer

#include <iostream>
using namespace std;

int main(a)
{
	// the pointer variable p refers to the space with the memory address numbered 0x1100
	int * p = (int *)0x1100;

	// Access the wild pointer
	cout << *p << endl; / / an error

    return 0;
}
// Neither the null pointer nor the wild pointer is our requested space, so do not access it
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