What does NULL mean in c language?

NULL is a null pointer constant in C language, used to prevent wild pointers and check pointer validity. Secondly, NULL is defined as (void *)0, which represents a pointer to a null address, which is different from 0 which represents an integer constant. When used only for pointer types, you need to check whether it is NULL first to avoid undefined behavior.

NULL in C language

The definition of NULL
NULL is C A special constant in the language that represents a null pointer value.

Purpose of NULL

• Initialize pointer variable: When declaring a pointer variable, initialize it to NULL to prevent wild pointers 's appearance.
• Check if the pointer is NULL: Before using a pointer, you should check if it is NULL to avoid pointing to undefined memory.
• As a function parameter: NULL can be passed as a function parameter, indicating no parameters.

Implementation of NULL

In C language, NULL is usually defined as (void *)0, indicating a pointer to null A null pointer to the address.

The difference between NULL and 0

Although NULL and 0 are numerically equal, they are conceptually different. NULL represents a null pointer, and 0 is an integer constant. In C language, NULL is a special constant and 0 is just an ordinary integer.

Things to note when using NULL

• Use NULL only for variables of pointer type.
• Always check if a pointer is NULL before using it.
• Do not dereference NULL as this causes undefined behavior.

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