在C/C++中可以使用多种形式表示和存储的字符串。最常见的基本的字符串表示形式（即C标准库/C++标准库都使用的形式）通称为C风格字符串，ISO C++的学名是NTCTS(null terminated character string)。
ISO C++11 17.3.17 [defns.ntcts]
NTCTS
a sequence of values that have character type that precede the terminating null character type value charT()
具体说来，一个典型的场景是：多余一个元素的char/wchar_t/char16_t/char32_t/其它实现允许的扩展字符类型的数组可以放一个NTCTS。
注意，a sequence of values而不是characters，表示抽象的含义。下面会看到character（但不是multibyte character）在C++标准库中的明确受限的意义。
顺便，关于multibyte character是C++整体通用的基本术语之一，所以独立于character之外考虑：
ISO C++11 1.3.13 [defns.multibyte]
multibyte character
sequence of one or more bytes representing a member of the extended character set of either the source or the execution environment
[ Note: The extended character set is a superset of the basic character set (2.3).—end note ]
（至于字符、基本执行字符集什么的虽然是必要基础但理解起来很简单，暂且不在此展开。）
ISO C++11 17.5.2.1.4 Character sequences [character.seq]
1 The C standard library makes widespread use of characters and character sequences that follow a few uniform conventions:
— A letter is any of the 26 lowercase or 26 uppercase letters in the basic execution character set.166
— The decimal-point character is the (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 Clauses 18 through 30 and Annex D by a period, ’.’, which is also its value in the "C" locale, but may change during program execution by a call to setlocale(int, const char*),167 or by a change to a locale object, as described in Clauses 22.3 and 27.
作者: 哦啊啊 时间: 2016-9-27 22:47
— A character sequence is an array object (8.3.4) A that can be declared as T A [N], where T is any of the types char, unsigned char, or signed char (3.9.1), 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.
166) Note that this definition differs from the definition in ISO C 7.1.1.
167) declared in <clocale> (22.6).
据此可以定义更具体的NTBS(null terminated byte string)
ISO C++11 17.5.2.1.4.1 Byte strings [byte.strings]
1 A null-terminated byte string, or NTBS, is a character sequence whose highest-addressed element with defined content has the value zero (the terminating null character); no other element in the sequence has the value zero.168
2 The length of an NTBS is the number of elements that precede the terminating null character. An empty ntbs has a length of zero.
3 The value of an NTBS is the sequence of values of the elements up to and including the terminating null character.
4 A static NTBS is an ntbs with static storage duration.169
168) Many of the objects manipulated by function signatures declared in <cstring> (21.7) 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.
169) A string literal, such as "abc", is a static ntbs.
ISO C++11 17.5.2.1.4.2 Multibyte strings [multibyte.strings]
1 A null-terminated multibyte string, or NTMBS, is an NTBS that constitutes a sequence of valid multibyte characters, beginning and ending in the initial shift state.170
2 A static NTMBS is an NTMBS with static storage duration.
170) An NTBS that contains characters only from the basic execution character set is also an NTMBS. Each multibyte character then consists of a single byte.
可见NTMBS是NTBS的子集，它其中可以包含多个（连续）字节组成的字符。
按17.5.2.1.4.1/2，NTMBS即NTBS的长度是其中包含的元素数。这里的“元素”概念和NTBS中有区别，即强调作为NTMBS时长度是多字节字符数而不是字符（字节）数。显然对于一般的NTMBS，即便去除结尾的空字符，长度和占用的字节数可以不同。
但是，ISO C里面关于“长度”可以有些关键性的不同。简而言之，ISO C标准库使用的string相当于NTBS，类似NTMBS的概念中长度仍以字节计：
ISO C99/C11(N1570)
7.1.1/1 A string is a contiguous sequence of characters terminated by and including the first null character. The term multibyte string is sometimes used instead to emphasize special processing given to multibyte characters contained in the string or to avoid confusion with a wide string. A pointer to a string is a pointer to its initial (lowest addressed) character. The length of a string is the number of bytes preceding the null character and the value of a string is the sequence of the values of the contained characters, in order.作者: chenhao597 时间: 2016-9-28 23:39
楼主你到底说是什么哦 思路好乱