Null Pointer In C

 

Null Pointers Definition :

A pointer that doesn’t point to any memory location is called a Null Pointer in C.It saves the segment’s base address.While void is the pointer’s type, the null pointer essentially holds the Null value.

Call by reference vs Call by value

Syntax :

int * ptr = NULL;

Null Pointers :

A pointer is referred to as a null pointer if there is no address that can be allocated to it. The pointer is regarded as a Null pointer when a NULL value is assigned to it.

 

Example :

Run
#include<stdio.h>
void main ()
{
    int val1, val2;
    int *ptr =  0;  
    if (ptr == 0)
    {
        ptr = &val1;
        val1 = 5;
    }
    if (ptr ==  0)    
    {
        ptr = &val2;
        val2 = 10;
    }
    printf ("value of *ptr: %d ", *ptr);
}

Output :

value of *ptr: 5

Uses of Null Pointers :

  • used to initialise a pointer variable when no proper memory address has yet been assigned to it.
  • used to pass a null pointer as a function argument when no valid memory address should be passed.
  • prior to accessing any pointer variable, used to check for a null pointer.
    In order to handle errors in pointer-related code, for example, dereference pointer variables only if they are not NULL.

Application of Null Pointers in C :

 
  • When the pointer variable is not given a memory address
  • While using malloc() function, we use Null Pointers.
  • You should validate a pointer before dereferencing it. It stops unpredictable behaviour .It helps in handling errors as well.

Example :

Run
#include<stdio.h>
int main()
{
    int * ptr =NULL;       // declaration of null pointer
    if(ptr!=NULL)
    {
        printf("Value of ptr is : %d",* ptr);
    }
    else
    {
        printf("Pointer is invalid");
    }
    return 0;
}

Output :

Pointer is invalid

Prime Course Trailer

Related Banners

Get PrepInsta Prime & get Access to all 200+ courses offered by PrepInsta in One Subscription

Get over 200+ course One Subscription

Courses like AI/ML, Cloud Computing, Ethical Hacking, C, C++, Java, Python, DSA (All Languages), Competitive Coding (All Languages), TCS, Infosys, Wipro, Amazon, DBMS, SQL and others

Checkout list of all the video courses in PrepInsta Prime Subscription

Checkout list of all the video courses in PrepInsta Prime Subscription