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The ability to represent a null character does not always mean the resulting string will be correctly interpreted, as many programs will consider the null to be the end of the string. Thus the ability to type it (in case of unchecked user input) creates a vulnerability known as null byte injection and can lead to security exploits. [10]
For example, the null character (U+0000 NULL) is used in C-programming application environments to indicate the end of a string of characters. In this way, these programs only require a single starting memory address for a string (as opposed to a starting address and a length), since the string ends once the program reads the null character.
The BSD documentation has been fixed to make this clear, but POSIX, Linux, and Windows documentation still uses "character" in many places where "byte" or "wchar_t" is the correct term. Functions for handling memory buffers can process sequences of bytes that include null-byte as part of the data.
Some three-digit octal escape sequences are too large to fit in a single byte. This results in an implementation-defined value for the resulting byte. The escape sequence \0 is a commonly used octal escape sequence, which denotes the null character, with value zero in ASCII and most encoding systems.
Null-terminated strings require that the encoding does not use a zero byte (0x00) anywhere; therefore it is not possible to store every possible ASCII or UTF-8 string. [ 8 ] [ 9 ] [ 10 ] However, it is common to store the subset of ASCII or UTF-8 – every character except NUL – in null-terminated strings.
A null pointer has a value reserved for indicating that the pointer does not refer to a valid object. Null pointers are routinely used to represent conditions such as the end of a list of unknown length or the failure to perform some action; this use of null pointers can be compared to nullable types and to the Nothing value in an option type.
In 1973, ECMA-35 and ISO 2022 [18] attempted to define a method so an 8-bit "extended ASCII" code could be converted to a corresponding 7-bit code, and vice versa. [19] In a 7-bit environment, the Shift Out would change the meaning of the 96 bytes 0x20 through 0x7F [a] [21] (i.e. all but the C0 control codes), to be the characters that an 8-bit environment would print if it used the same code ...
Microsoft was one of the first companies to implement Unicode in their products. Windows NT was the first operating system that used "wide characters" in system calls.Using the (now obsolete) UCS-2 encoding scheme at first, it was upgraded to the variable-width encoding UTF-16 starting with Windows 2000, allowing a representation of additional planes with surrogate pairs.