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Each string ends at the first occurrence of the zero code unit of the appropriate kind (char or wchar_t).Consequently, a byte string (char*) can contain non-NUL characters in ASCII or any ASCII extension, but not characters in encodings such as UTF-16 (even though a 16-bit code unit might be nonzero, its high or low byte might be zero).
While std::string standardized strings, legacy applications still commonly contain such custom string types and libraries may expect C-style strings, making it "virtually impossible" to avoid using multiple string types in C++ programs [1] and requiring programmers to decide on the desired string representation ahead of starting a project. [4]
Both character termination and length codes limit strings: For example, C character arrays that contain null (NUL) characters cannot be handled directly by C string library functions: Strings using a length code are limited to the maximum value of the length code. Both of these limitations can be overcome by clever programming.
A character literal is a type of literal in programming for the representation of a single character's value within the source code of a computer program. Languages that have a dedicated character data type generally include character literals; these include C , C++ , Java , [ 1 ] and Visual Basic . [ 2 ]
The length of a string is found by searching for the (first) NUL. This can be slow as it takes O(n) (linear time) with respect to the string length. It also means that a string cannot contain a NUL (there is a NUL in memory, but it is after the last character, not in the string).
This is because string literals have array type, char [n] (C) or const char [n] (C++), which cannot be added; this is not a restriction in most other languages. This is particularly important when used in combination with the C preprocessor, to allow strings to be computed following preprocessing, particularly in macros. [13] As a simple example:
find_character(string,char) returns integer Description Returns the position of the start of the first occurrence of the character char in string. If the character is not found most of these routines return an invalid index value – -1 where indexes are 0-based, 0 where they are 1-based – or some value to be interpreted as Boolean FALSE.
Recent versions of these standards refer to char as a numeric type. char is also used for a 16-bit integer type in Java, but again this is not a Unicode character type. [25] The term string also does not always refer to a sequence of Unicode