16 Library introduction [library]

16.3 Method of description [description]

16.3.3 Other conventions [conventions] Type descriptions [type.descriptions] Character sequences [character.seq] General [character.seq.general]

The C standard library makes widespread use of characters and character sequences that follow a few uniform conventions:
  • Properties specified as locale-specific may change during program execution by a call to setlocale(int, const char*) ([clocale.syn]), or by a change to a locale object, as described in [locales] and [input.output].
  • The execution character set and the execution wide-character set are supersets of the basic literal character set ([lex.charset]).
    The encodings of the execution character sets and the sets of additional elements (if any) are locale-specific.
    Each element of the execution wide-character set is encoded as a single code unit representable by a value of type wchar_t.
    [Note 1: 
    The encodings of the execution character sets can be unrelated to any literal encoding.
    — end note]
  • A letter is any of the 26 lowercase or 26 uppercase letters in the basic character set.
  • The decimal-point character is the locale-specific (single-byte) character used by functions that convert between a (single-byte) character sequence and a value of one of the floating-point types.
    It is used in the character sequence to denote the beginning of a fractional part.
    It is represented in [support] through [thread] and [depr] by a period, '.', which is also its value in the "C" locale.
  • A character sequence is an array object A that can be declared as T A[N], where T is any of the types char, unsigned char, or signed char ([basic.fundamental]), optionally qualified by any combination of const or volatile.
    The initial elements of the array have defined contents up to and including an element determined by some predicate.
    A character sequence can be designated by a pointer value S that points to its first element.