NULL is a reserved value in calculation, indicating that the pointer does not point to a valid object. Programs usually use null pointers to indicate conditions, such as the end of an unknown length list or the inability to perform certain operations; The use of this null pointer can be compared with the Nothing value in nullable types and option types.
A null pointer should not be confused with an uninitialized pointer: a null pointer will definitely be compared with any pointer to a valid object. However, depending on the language and implementation, uninitialized pointers may not have any such guarantee. It may be equal to other valid pointers; Or it may be more like an empty pointer. It may do two things at different times.
Extended data:
Null characters are usually represented as source code string characters or escape sequences in character constants. In many languages, this is not a single escape sequence, but a single octal escape sequence with octal number 0.
Therefore, "\ 0" cannot follow any number between 0 and 7; Otherwise, it is interpreted as the beginning of a longer octal escape sequence. Unicode representation of other escape sequences \000, \x00, \z or \u0000 in various languages.
The ability to represent null characters does not always mean that the generated string will be interpreted correctly, because many programs regard null as the end of the string. Therefore, the ability to type it (in the case of unchecked user input) will create a vulnerability called null byte injection and may lead to security vulnerabilities.
Empty characters are denoted by commas as @. On Windows, you Ctrl press @ (this usually requires pressing? Shift and press the number key 2).
Empty characters in a document are sometimes represented as a single EM containing the width symbol of the letter "NUL". In Unicode, a character has a corresponding character, which is used for the visual representation of empty characters. The "empty" symbol, U+2400 (? ), but don't confuse it with the actual empty character U+0000.
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