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In C, two null pointers of any type are guaranteed to compare equal. [3] Prior to C23, the preprocessor macro NULL was provided, defined as an implementation-defined null pointer constant in <stdlib.h>, [4] which in C99 can be portably expressed as ((void *)0), the integer value 0 converted to the type void* (see pointer to void type). [5]
sizeof is a unary operator in the programming languages C and C++. It generates the storage size of an expression or a data type, measured in the number of char-sized units. Consequently, the construct sizeof (char) is guaranteed to be 1.
The maximum size of size_t is provided via SIZE_MAX, a macro constant which is defined in the <stdint.h> header (cstdint header in C++). size_t is guaranteed to be at least 16 bits wide. Additionally, POSIX includes ssize_t , which is a signed integer type of the same width as size_t .
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 ).
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
Null-terminated strings were produced by the .ASCIZ directive of the PDP-11 assembly languages and the ASCIZ directive of the MACRO-10 macro assembly language for the PDP-10. These predate the development of the C programming language, but other forms of strings were often used.
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".
Byte, octet, minimum size of char in C99( see limits.h CHAR_BIT) −128 to +127 0 to 255 2 bytes 16 bits x86 word, minimum size of short and int in C −32,768 to +32,767 0 to 65,535 4 bytes 32 bits x86 double word, minimum size of long in C, actual size of int for most modern C compilers, [8] pointer for IA-32-compatible processors