GeeksforGeeks
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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
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 −
Checking for NULL pointer in C/C++ - Stack Overflow
So if you want to check a pointer, better to do "if (ptr != NULL)" instead of "if (ptr)". If you mistakenly declare ptr as an int, the first check will raise a warning/error, while the latter will compile without any warning. 2014-11-05T09:21:23.753Z+00:00 ... @David天宇Wong No, that is not what was meant. The example ... More on stackoverflow.com
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
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August 30, 2024Trying 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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December 30, 2021What is Null?
NULL is nothing. It means theres nothing there. Often its just a place holder before something is there. Say u have a bunch of variables of animals. U might set them to NULL before u know what they are. Then u might check if they are NULL before u add an animal to them. Things are initialized as NULL. More on reddit.com
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July 5, 2024What 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
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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
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
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Null Pointer in C Language (Uses, Best Practices, Examples)
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What is Null Pointer in C. #pointer #cprogramming #gcc - YouTube
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NULL Pointer | C Programming Tutorial - YouTube
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Null Pointers In C Programming Language - YouTube
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What is a C++ null pointer? ⛔ - YouTube
Unstop
unstop.com › home › blog › null pointer in c | a detailed explanation with examples
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. This example shows why it is important to check if the NULL pointer was successfully created in dynamic memory allocation.
WsCube Tech
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
includehelp.com › c-programs › an-example-of-null-pointer-in-c.aspx
An Example of Null pointer in C
March 10, 2024 - ptr1 is initialized with the address of the integer variable num, thus ptr1 contains a valid memory address. ptr2 is uninitialized and ptr3 assigned 0. Thus, ptr2 and ptr3 are the NULL pointers.
W3Schools
w3schools.com › c › c_null.php
C NULL
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.
EDUCBA
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Null pointer in C | How Null pointer work in C with Examples
March 28, 2023 - Explanation: In the above code, we are initializing the variable “ptr” to 0 (zero) so when we print the pointer value which Null pointer. Suppose let us take another example where the pointer variables are not assigned to any memory address.
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Codecademy
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:
Scaler
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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 - Null pointers are a key part of many data structures and algorithms in C. In the below example, we declare the pointer variable *ptr, but it does not contain the address of any variable.
Javatpoint
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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.
CodeWithHarry
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NULL Pointer | C Tutorial | CodeWithHarry
NULL pointers and void pointers very much sound similar just because of their nomenclatures, but they are very different as a NULL pointer is a pointer with a NULL value address, and a void pointer is a pointer of void data type. Their significances are contrasting. ... Here, an integer pointer variable is declared with a value NULL, which means it is not pointing to any memory location.
Lysator
lysator.liu.se › c › c-faq › c-1.html
Null Pointers
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
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NULL pointer in C - IncludeHelp
NULL is a predefined Macro, and ... that is assigned with NULL Macro. ... In the given statement ptr is an integer pointer which is being initialized with NULL, thus ptr will be considered as NULL pointer....
LabEx
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Using Null Pointer in C Programming
A null pointer is a pointer that does not point to any memory address. In C programming, a null pointer is represented by the constant NULL, which is defined in the header file stdio.h.
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In my experience, tests of the form if (ptr) or if (!ptr) are preferred. They do not depend on the definition of the symbol NULL. They do not expose the opportunity for the accidental assignment. And they are clear and succinct.
Edit: As SoapBox points out in a comment, they are compatible with C++ classes such as unique_ptr, shared_ptr, auto_ptr that are objects that act as pointers and which provide a conversion to bool to enable exactly this idiom. For these objects, an explicit comparison to NULL would have to invoke a conversion to pointer which may have other semantic side effects or be more expensive than the simple existence check that the bool conversion implies.
I have a preference for code that says what it means without unneeded text. if (ptr != NULL) has the same meaning as if (ptr) but at the cost of redundant specificity. The next logical thing is to write if ((ptr != NULL) == TRUE) and that way lies madness. The C language is clear that a boolean tested by if, while or the like has a specific meaning of non-zero value is true and zero is false. Redundancy does not make it clearer.
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if (foo) is clear enough. Use it.
GNU
gnu.org › software › c-intro-and-ref › manual › html_node › Null-Pointers.html
Null Pointers (GNU C Language Manual)
A pointer value can be null, which means it does not point to any object. The cleanest way to get a null pointer is by writing NULL, a standard macro defined in stddef.h. You can also do it by casting 0 to the desired pointer type, as in (char *) 0.
Naukri
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Null Pointer in C - Naukri Code 360
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Shishirkant
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....
Aticleworld
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What is a Null Pointer in C/C++? - Aticleworld
January 25, 2023 - That means your program might not work as its implementation or it might be crashed. ... #include<stdio.h> int main() { //ptr pointing some unknown memory location int *ptr; //Assigning value *ptr = 12; printf("%d\n",*ptr); return 0; }