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cppdraft/character/seq.md

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+[character.seq]
+
+# 16 Library introduction [[library]](./#library)
+
+## 16.3 Method of description [[description]](description#character.seq)
+
+### 16.3.3 Other conventions [[conventions]](conventions#character.seq)
+
+#### 16.3.3.3 Type descriptions [[type.descriptions]](type.descriptions#character.seq)
+
+#### 16.3.3.3.4 Character sequences [character.seq]
+
+#### [16.3.3.3.4.1](#general) General [[character.seq.general]](character.seq.general)
+
+[1](#general-1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L720)
+
+The C standard library makes widespread useof characters and character sequences that follow a few uniform conventions:
+
+- [(1.1)](#general-1.1)
+
+  Properties specified as [*locale-specific*](#def:locale-specific "16.3.3.3.4.1 General [character.seq.general]") may change during program execution
+by a call to setlocale(int, const char*) ([[clocale.syn]](clocale.syn "28.3.5.1 Header <clocale> synopsis")), or
+by a change to a locale object,
+as described in [[locales]](locales "28.3.3 Locales") and [[input.output]](input.output "31 Input/output library")[.](#general-1.1.sentence-1)
+
+- [(1.2)](#general-1.2)
+
+  The [*execution character set*](#def:character_set,execution "16.3.3.3.4.1 General [character.seq.general]") and
+the [*execution wide-character set*](#def:wide-character_set,execution "16.3.3.3.4.1 General [character.seq.general]") are supersets of the basic literal character set ([[lex.charset]](lex.charset "5.3.1 Character sets"))[.](#general-1.2.sentence-1)
+  The encodings of the execution character sets and
+the sets of additional elements (if any) are locale-specific[.](#general-1.2.sentence-2)
+  Each element of the execution wide-character set is encoded as
+a single code unit representable by a value of type wchar_t[.](#general-1.2.sentence-3)
+  [*Note [1](#general-note-1)*:
+  The encodings of the execution character sets can be unrelated
+to any literal encoding[.](#general-1.2.sentence-4)
+ — *end note*]
+
+- [(1.3)](#general-1.3)
+
+  A [*letter*](#def:letter "16.3.3.3.4.1 General [character.seq.general]") is any of the 26 lowercase or 26uppercase letters in the basic character set[.](#general-1.3.sentence-1)
+
+- [(1.4)](#general-1.4)
+
+  The[*decimal-point character*](#def:character,decimal-point "16.3.3.3.4.1 General [character.seq.general]") 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[.](#general-1.4.sentence-1)
+  It is used
+in the character sequence to denote the beginning of a fractional part[.](#general-1.4.sentence-2)
+  It is
+represented in [[support]](support "17 Language support library") through [[exec]](exec "33 Execution control library") and [[depr]](depr "Annex D (normative) Compatibility features") by a period,'.',
+which is
+also its value in the "C" locale[.](#general-1.4.sentence-3)
+
+- [(1.5)](#general-1.5)
+
+  A[*character sequence*](#def:character_sequence "16.3.3.3.4.1 General [character.seq.general]") is an [array object](dcl.array "9.3.4.5 Arrays [dcl.array]") *A* that
+can be declared as*T A*[*N*],
+where *T* is any of the typeschar,unsigned char,
+orsigned char ([[basic.fundamental]](basic.fundamental "6.9.2 Fundamental types")), optionally qualified by any combination ofconst orvolatile[.](#general-1.5.sentence-1)
+  The initial elements of the
+array have defined contents up to and including an element determined by some
+predicate[.](#general-1.5.sentence-2)
+  A character sequence can be designated by a pointer value*S* that points to its first element[.](#general-1.5.sentence-3)
+
+#### [16.3.3.3.4.2](#byte.strings) Byte strings [[byte.strings]](byte.strings)
+
+[1](#byte.strings-1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L788)
+
+A [*null-terminated byte string*](#def:ntbs "16.3.3.3.4.2 Byte strings [byte.strings]"),
+or ntbs,
+is a character sequence whose highest-addressed element
+with defined content has the value zero
+(the [*terminating null character*](#def:character,terminating_null "16.3.3.3.4.2 Byte strings [byte.strings]"));
+no other element in the sequence has the value zero[.](#byte.strings-1.sentence-1)[139](#footnote-139 "Many of the objects manipulated by function signatures declared in <cstring> are character sequences or ntbss. The size of some of these character sequences is limited by a length value, maintained separately from the character sequence.")
+
+[2](#byte.strings-2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L803)
+
+The [*length of an ntbs*](#def:ntbs,length "16.3.3.3.4.2 Byte strings [byte.strings]") is the number of elements that
+precede the terminating null character[.](#byte.strings-2.sentence-1)
+
+An [*empty ntbs*](#def:ntbs,empty "16.3.3.3.4.2 Byte strings [byte.strings]") has a length of zero[.](#byte.strings-2.sentence-2)
+
+[3](#byte.strings-3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L810)
+
+The [*value of an ntbs*](#def:ntbs,value "16.3.3.3.4.2 Byte strings [byte.strings]") is the sequence of values of the
+elements up to and including the terminating null character[.](#byte.strings-3.sentence-1)
+
+[4](#byte.strings-4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L815)
+
+A [*static ntbs*](#def:ntbs,static "16.3.3.3.4.2 Byte strings [byte.strings]") is an ntbs with
+static storage duration[.](#byte.strings-4.sentence-1)[140](#footnote-140 "A string-literal, such as &quot;abc&quot;, is a static ntbs.")
+
+[139)](#footnote-139)[139)](#footnoteref-139)
+
+Many of the objects manipulated by
+function signatures declared in[<cstring>](cstring.syn#header:%3ccstring%3e "27.5.1 Header <cstring> synopsis [cstring.syn]") are character sequences or ntbss[.](#footnote-139.sentence-1)
+
+The size of some of these character sequences is limited by
+a length value, maintained separately from the character sequence[.](#footnote-139.sentence-2)
+
+[140)](#footnote-140)[140)](#footnoteref-140)
+
+A [*string-literal*](lex.string#nt:string-literal "5.13.5 String literals [lex.string]"), such as"abc",
+is a static ntbs[.](#footnote-140.sentence-1)
+
+#### [16.3.3.3.4.3](#multibyte.strings) Multibyte strings [[multibyte.strings]](multibyte.strings)
+
+[1](#multibyte.strings-1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L827)
+
+A [*multibyte character*](#def:character,multibyte "16.3.3.3.4.3 Multibyte strings [multibyte.strings]") is
+a sequence of one or more bytes representing the
+code unit sequence for an encoded character of the
+execution character set[.](#multibyte.strings-1.sentence-1)
+
+[2](#multibyte.strings-2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L834)
+
+A [*null-terminated multibyte string*](#def:ntmbs "16.3.3.3.4.3 Multibyte strings [multibyte.strings]"),
+or ntmbs,
+is an ntbs that constitutes a
+sequence of valid multibyte characters, beginning and ending in the initial
+shift state[.](#multibyte.strings-2.sentence-1)[141](#footnote-141 "An ntbs that contains characters only from the basic literal character set is also an ntmbs. Each multibyte character then consists of a single byte.")
+
+[3](#multibyte.strings-3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L847)
+
+A [*static ntmbs*](#def:ntmbs,static "16.3.3.3.4.3 Multibyte strings [multibyte.strings]") is an ntmbs with static storage duration[.](#multibyte.strings-3.sentence-1)
+
+[141)](#footnote-141)[141)](#footnoteref-141)
+
+An ntbs that contains characters only from the
+basic literal character set is also an ntmbs[.](#footnote-141.sentence-1)
+
+Each multibyte character then
+consists of a single byte[.](#footnote-141.sentence-2)