NULL (CRT) (2024)

FAQs

Where is NULL defined in C? ›

NULL is defined in the following header files: CRTDBG. H, LOCALE. H, STDDEF. H, STDIO.

The NULL macro is defined in <stddef. h> . (It is also defined in several other headers.) It expands to a null pointer constant and is intended to be used with pointers, not with characters.

The stddef. h header defines the macros NULL and offsetof . NULL is a pointer that never points to a data object. The offsetof macro expands to the number of bytes between a structure member and the start of the structure.

The C and C++ languages have a null character (NUL), a null pointer (NULL), and a null statement (just a semicolon (;)). The C NUL is a single character that compares equal to 0. The C NULL is a special reserved pointer value that does not point to any valid data object.

A Null pointer is a variable in the C programming language that has a value of zero or has an address that points to nothing. In C, we use the keyword NULL to make a variable a null pointer, which is a predefined macro.

In computer programming, null is both a value and a pointer. Null is a built-in constant that has a value of zero. It is the same as the character 0 used to terminate strings in C. Null can also be the value of a pointer, which is the same as zero unless the CPU supports a special bit pattern for a null pointer.

The NULL macro expands to a null pointer constant, such as 0 or 0L . Some C libraries declare NULL as ((void*)0) in stddef. h.

The value of NULL , (0) , is implicitly converted to the destination type. The 32-bit compilers previously assigned NULL the expression ((void *)0) . No action required.

What does %*c mean in C/C++ programming? When passed as part of a `scanf` format string, “%*c” means “read and ignore a character”. There has to be a character there for the conversion to succeed, but other than that, the character is ignored.

h is the header of the general purpose standard library of C programming language which includes functions involving memory allocation, process control, conversions and others. It is compatible with C++ and is known as cstdlib in C++. The name "stdlib" stands for "standard library".

What is the Size_t in C? ›

size_t is a special unsigned integer type defined in the standard library of C and C++ languages. It is the type of the result returned by the sizeof and alignof operators. The size_t is chosen so that it can store the maximum size of a theoretically possible array or an object.

In C, and many other low-level programming languages the term NULL is equivalent to 0 . The C standard requires NULL to be #define d to an "implementation defined value", however all implementations have chosen (for obvious reasons) to use 0 for that purpose.

This happens because NULL is not a built-in constant in the C or C++ languages. In fact, in C++, it's more or less obsolete, instead, just a plain 0 is used.

The Null Character in C is represented using the escape sequence '\0'. It is essential to distinguish it from the character '0' to prevent potential bugs in string handling. For example, when initializing a character array or a string, it is common to terminate the sequence with a Null Character to mark its end.

A simple if (ptr) tests whether ptr is TRUE. It will return FALSE if ptr is NULL, or if ptr is 0.