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NULL Pointer in C - GeeksforGeeks

We just have to assign the NULL value. Strictly speaking, NULL expands to an implementation-defined null pointer constant which is defined in many header files such as “stdio.h”, “stddef.h”, “stdlib.h” etc.

Published: January 10, 2025

tutorialspoint.com › cprogramming › c_null_pointer.htm

NULL Pointer in C

Checking if the FILE pointer returned by the fopen() function is NULL is always a recommended approach to avoid runtime errors in file-related processing. The following example shows how you can use the NULL file pointer to ensure that a file is accessible or not −

Discussions

Why do we use Null pointers?

The value where a null pointer is pointing is irrelevant. A null pointer is a pointer that is pointing nowhere--there is no value. In C, the number 0 was defined as the representation of the null pointer. They could have picked any number, but it would have been painful. More on reddit.com

r/C_Programming

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August 30, 2024

Trying to understand NULL pointers

NULL is equivalent to 0 and equivalent to nullptr (in C++). It's an address that is "universally invalid." You can store 0x2093704802934 in a pointer and it will be invalid too (I'm sure) but it's not a convention. NULL is this convention that says "the pointer is not valid" and/or "the pointer hasn't been initialized yet" or "the memory pointed to has been released and I have invalidated the pointer by setting it to NULL." You store this value in a "pointer", like "int* s = 0" to show that it is not pointing to anything. And in your code you will check whether the pointer (s in my example) is equal to NULL (invalid) or not (valid). First you create a pointer, then you initialize it, then you use it, then you release it. More on reddit.com

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People also ask

What is the value of a null pointer in C?

The value is NULL, which is usually defined as ((void *)0) or 0, depending on the system.

wscubetech.com › resources › c-programming › null-pointer

Null Pointer in C Language (Uses, Best Practices, Examples)

What’s the size of a null pointer in C?

The size is the same as any other pointer of the same type (typically 4 bytes in 32-bit systems, 8 bytes in 64-bit).

wscubetech.com › resources › c-programming › null-pointer

Null Pointer in C Language (Uses, Best Practices, Examples)

How to check if a pointer is NULL in C?

You can check whether a pointer is NULL by using an if condition before accessing it to ensure it points to valid memory. For example, if (ptr == NULL) checks whether the pointer is empty before using it.

wscubetech.com › resources › c-programming › null-pointer

Null Pointer in C Language (Uses, Best Practices, Examples)

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Null Pointer In C | A Detailed Explanation With Examples

May 3, 2024 - The incorrectUse() function directly dereferences the pointer without checking if it's NULL. This results in undefined behavior because we're attempting to access memory that doesn't exist.

wscubetech.com › resources › c-programming › null-pointer

Null Pointer in C Language (Uses, Best Practices, Examples)

July 27, 2026 - Learn in this tutorial about the null pointer in C, including its syntax, uses, how to check it, best practices, and examples to write efficient programs.

includehelp.com › c-programs › an-example-of-null-pointer-in-c.aspx

An Example of Null pointer in C

March 10, 2024 - #include <stdio.h> int main(void) { int num = 10; int *ptr1 = &num; int *ptr2; int *ptr3=0; if(ptr1 == 0) printf("ptr1: NULL\n"); else printf("ptr1: NOT NULL\n"); if(ptr2 == 0) printf("ptr2: NULL\n"); else printf("ptr2: NOT NULL\n"); if(ptr3 == 0) printf("ptr3: NULL\n"); else printf("ptr3: NOT NULL\n"); return 0; } ... C program to read and print student details using structure pointer, demonstrate example of structure with pointer

w3schools.com › c › c_null.php

You can compare a pointer to NULL to check if it is safe to use. Many C functions return NULL when something goes wrong. For example, fopen() returns NULL if a file cannot be opened, and malloc() returns NULL if memory allocation fails.

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Null pointer in C | How Null pointer work in C with Examples

March 28, 2023 - So usually when we try to write or read from a null pointer we get run time error as we saw in the above code which we get segmentation fault which is a null pointer exception sometimes it also throws an exception as null pointer exception. In most of the examples, a null pointer is used to denote or indicate the end of the list.

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codecademy.com › docs › pointers › null pointer

C | Pointers | Null Pointer | Codecademy

February 3, 2025 - In C, the NULL pointer is defined in the <stddef.h> header file. It is typically assigned to a pointer to indicate that it is not pointing to any valid memory. #include <stddef.h> pointer_type *pointer_name = NULL; ... In the example, we declare an integer pointer ptr and initialize it to NULL, indicating that it doesn’t point to any valid memory location:

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What is Null Pointer in C? - Scaler Topics

September 4, 2023 - We can overcome the above problem ... memory area that can't be dereferenced. In the example below, We create a pointer *ptr and assign it the value NULL to indicate that it doesn't point to any variables....

Dot Net Tutorials

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Null Pointer in C Language with Examples - Dot Net Tutorials

November 16, 2023 - A null pointer points to the 0th memory location, a reserved memory that cannot be dereferenced. In the below example, we create a pointer *ptr and assign a NULL value to the pointer, which means that it does not point ...

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Null Pointer in C - javatpoint

Null Pointer in C with programming examples for beginners and professionals covering concepts, control statements, c array, c pointers, c structures, c union, c strings and more.

lysator.liu.se › c › c-faq › c-1.html

If the (char *) cast were omitted, the compiler would not know to pass a null pointer, and would pass an integer 0 instead. (Note that many Unix manuals get this example wrong.)

includehelp.com › c › null-pointer.aspx

NULL pointer in C - IncludeHelp

C language NULL pointer explanation with example, here we will learn about the NULL Macro and NULL pointer with their declaration and usages.

shishirkant.com › null-pointer-in-c-programming

Null Pointer in C Programming – Shishir Kant Singh

In C Programming Language, we can ... memory and cannot be dereferenced. In the below example, we create a pointer *ptr and assign a NULL value to the pointer, which means that it does not point to any variable....

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Null Pointer In C

January 17, 2023 - #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; } ... Courses like AI/ML, Cloud Computing, Ethical Hacking, ...

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Null Pointer in C C Programming | StudyMite

August 2, 2026 - When we run this code, we get the ... libraries. We get the output as 0, which indicates that the pointer does not intend to point to any accessible memory location i.e. it intends to point to nothing....

codewithharry.com › tutorial › c-null-pointer

NULL Pointer | C Tutorial | CodeWithHarry

The dereferencing behavior of a NULL pointer is very much similar to that of a void pointer. A NULL pointer itself is a kind of a VOID pointer and hence, we have to typecast it into any data type the way we do to a void pointer before dereferencing. Failing to do so results in an error at compile ...

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Null Pointer in C - Naukri Code 360

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en.wikipedia.org › wiki › Null_pointer

Null pointer - Wikipedia

June 13, 2026 - In practice, dereferencing a null pointer may result in an attempted read or write from memory that is not mapped, triggering a segmentation fault or memory access violation. This may manifest itself as a program crash, or be transformed into a software exception that can be caught by program code. There are, however, certain circumstances where this is not the case. For example...

C C++Other languages Null dereferencing Mitigation History

wikihow.com › computers and electronics › software › programming › c programming languages › how to check null in c: 7 steps (with pictures) - wikihow

How to Check Null in C: 7 Steps (with Pictures) - wikiHow

June 9, 2025 - Instead write: char *ptr = NULL; //This assigns the pointer to NULL if(ptr == NULL) { //This will return TRUE if the pointer has not been reassigned. } ... Pay attention to functions that could return NULL.