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In some programming language environments (at least one proprietary Lisp implementation, for example), [citation needed] the value used as the null pointer (called nil in Lisp) may actually be a pointer to a block of internal data useful to the implementation (but not explicitly reachable from user programs), thus allowing the same register to be used as a useful constant and a quick way of ...
Pointers in C programming Archived 2019-06-09 at the Wayback Machine A visual model for beginner C programmiers; 0pointer.de A terse list of minimum length source codes that dereference a null pointer in several different programming languages "The C book" – containing pointer examples in ANSI C
In object-oriented computer programming, a null object is an object with no referenced value or with defined neutral (null) behavior.The null object design pattern, which describes the uses of such objects and their behavior (or lack thereof), was first published as "Void Value" [1] and later in the Pattern Languages of Program Design book series as "Null Object".
To expose dangling pointer errors, one common programming technique is to set pointers to the null pointer or to an invalid address once the storage they point to has been released. When the null pointer is dereferenced (in most languages) the program will immediately terminate—there is no potential for data corruption or unpredictable behavior.
This is an accepted version of this page This is the accepted version, checked on 17 January 2025. There are template/file changes awaiting review. General-purpose programming language "C programming language" redirects here. For the book, see The C Programming Language. Not to be confused with C++ or C#. C Logotype used on the cover of the first edition of The C Programming Language Paradigm ...
In C, variables with static storage duration that are not initialized explicitly are initialized to zero (or null, for pointers). [ 3 ] Not only are uninitialized variables a frequent cause of bugs, but this kind of bug is particularly serious because it may not be reproducible: for instance, a variable may remain uninitialized only in some ...
It is often abbreviated as NUL (or NULL, though in some contexts that term is used for the null pointer). In 8-bit codes, it is known as a null byte . The original meaning of this character was like NOP —when sent to a printer or a terminal , it has no effect (some terminals, however, incorrectly display it as space ).
The C standard does not say that the null pointer is the same as the pointer to memory address 0, though that may be the case in practice. Most operating systems map the null pointer's address such that accessing it causes a segmentation fault. This behavior is not guaranteed by the C standard. Dereferencing a null pointer is undefined behavior ...