blocks|key|3065324|text|UNICODE标准是3.9节规定的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3065325|Unicode的每种编码形式都将|3065326|代码点U%2B0000..U%2BD7FF和U%2BE000..U%2B10FFFF映射到唯一的代码单元序列。|blockquote|3065327|3065328|3065329|因此，可以由UTF-16表示的代码点(‘字符’)的数量为|3065330|0xD7FF+%2B+1+%2B+(0x10FFFF+-+0xE000)+%2B+1+=+1+112+064|code-block|syntax|javascript|3065331|UNICODE标准通常是32位的。但是，特定编码保留较少的位数来表示最常见的字符，这对它们可以合法表示的实际字符数施加了特定限制。为了允许更长的比特序列，从而允许描述比8+(UTF-8)或16+(UTF-16)比特更长的码点，定义了特殊的代理码点。|3065332|此外，能够以给定的编码表示给定的代码点并不意味着它是有效的-它必须首先由UNICODE标准进行分配和描述。因此，没有一个数学公式可以计算出可以表示的字符数，1112064这个数字并不一定意味着有1M个有效字符。|3065333|有关详细讨论，请参阅UNICODE标准的section+3.9。|offset|length|3065334|entityMap|0|LINK|mutability|MUTABLE|url|http://www.unicode.org/versions/Unicode5.2.0/ch03.pdf#G7404^0|0|0|0|0|0|0|0|0|0|K|B|0|0^^$0|@$1|2|3|4|5|6|7|15|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|16|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|17|8|@]|9|@]|A|$]]|$1|G|3|-4|5|6|7|18|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|19|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|1A|8|@]|9|@]|A|$]]|$1|K|3|L|5|M|7|1B|8|@]|9|@]|A|$N|O]]|$1|P|3|Q|5|6|7|1C|8|@]|9|@]|A|$]]|$1|R|3|S|5|6|7|1D|8|@]|9|@]|A|$]]|$1|T|3|U|5|6|7|1E|8|@]|9|@$V|1F|W|1G|1|1H]]|A|$]]|$1|X|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]]|Y|$Z|$5|10|11|12|A|$13|14]]]]

The UNICODE standard is section 3.9 says: 

<blockquote>
 Each encoding form maps the Unicode code points U+0000..U+D7FF and U+E000..U+10FFFF to unique code unit sequences.
</blockquote>

Hence the number of code points ('characters') that can be represented by UTF-16 is

<pre><code>0xD7FF + 1 + (0x10FFFF - 0xE000) + 1 = 1 112 064
</code></pre>

The UNICODE standard is generally 32-bit. However, specific encodings reserve smaller amount of bits to represent the most common characters impose specific limitations on the real number of characters they can legally represent. To allow for longer bit sequences that in turn allow describing code points longer that 8 (UTF-8) or 16 (UTF-16) bits special surrogate code points are defined.

Also, being able to represent a given code point in the given encoding doesn't mean it is valid — it has to be allocated and described by the UNICODE standard first. Therefore there's no mathematical formula which would yield the number of characters that can be represented and the number 1 112 064 doesn't necessarily mean there are 1M valid characters.

For a detailed discussion see <a href="http://www.unicode.org/versions/Unicode5.2.0/ch03.pdf#G7404" rel="noreferrer">section 3.9</a> of the UNICODE standard.

blocks|key|1848557|text|不是的。由UTF-16表示的字符数只能通过规范知道，不能通过数学计算知道。UTF-16是人们制定的一组特定的编码规则，而不是某个公式的固有属性。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1848558|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

No. The number of characters represented by UTF-16 is only knowable by specification, not by mathematics. UTF-16 is a specific set of encoding rules laid out by people, not an intrinsic property of some formula.

blocks|key|3065272|text|请在此处查看答案https://stackoverflow.com/questions/280182/|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3065273|它几乎和规范一样好，嗯，它结合了一些规范。我引述如下：|3065274|3065275|+UTF-16是一种长度可变的代码；它的字符占用2或4个字节。0xD800-0xDFFF范围内的2字节值保留用于构造4字节字符，所有4字节字符由0xD800-0xDBFF范围内的2个字节和0xDC00-0xDFFF范围内的2个字节组成。因此，Unicode不会分配U%2BD800-U%2BDFFF范围内的任何字符。|blockquote|3065276|3065277|UTF-16的容量:+1,112,064|3065278|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/280182/^0|8|17|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|6|7|Y|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|Z|8|@]|9|@]|C|$]]|$1|G|3|H|5|I|7|10|8|@]|9|@]|C|$]]|$1|J|3|-4|5|6|7|11|8|@]|9|@]|C|$]]|$1|K|3|L|5|6|7|12|8|@]|9|@]|C|$]]|$1|M|3|-4|5|6|7|13|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]]]

See the answer here <a href="https://stackoverflow.com/questions/280182/">https://stackoverflow.com/questions/280182/</a>
It is almost as good as a specification, well, it combines some specifications. I'll quote:
<blockquote>
UTF-16 is a variable-length code; its characters consume either 2 or 4 bytes. 2-byte values in the range 0xD800-0xDFFF are reserved for constructing 4-byte characters, and all 4-byte characters consist of two bytes in the range 0xD800-0xDBFF followed by 2 bytes in the range 0xDC00-0xDFFF. For this reason, Unicode does not assign any characters in the range U+D800-U+DFFF.
Capacity of UTF-16: 1,112,064
</blockquote>

blocks|key|3065369|text|您可以在UTF-16中表示1112064个标量值，因为标准的第3.9节中的定义D76定义了1112064个标量值，而且UTF-16编码格式(与所有Unicode编码格式一样)是所有Unicode标量值的唯一表示形式，如定义D79中所定义的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3065370|Unicode+D76+-+Unicode标量值:除高代理代码点和低代理代码点之外的任何Unicode代码点。|3065371|3065372|3065373|由于此定义，Unicode标量值集合由范围0到D7FF和E000到10FFFF组成，包括0到10FFFF。|unordered-list-item|3065374|3065375|D79+-+Unicode编码形式将每个Unicode标量值分配给唯一的代码单元序列。|3065376|当然，由于definition+D91中列出的代理项对编码机制，这些数字并不是完全任意的。根据表3-5中的比特分布，没有办法对高于10FFFF的标量值进行编码。|3065377|entityMap^0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Q|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|R|8|@]|9|@]|A|$]]|$1|E|3|-4|5|6|7|S|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|T|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|U|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|V|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|W|8|@]|9|@]|A|$]]|$1|N|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|O|$]]

You can represent 1112064 scalar values in UTF-16 because there are 1112064 scalar values as defined by definition D76 in section 3.9 of the Standard, and because the UTF-16 encoding form (like all Unicode encoding forms) is a unique representation of all Unicode scalar values, as defined in definition D79.

<blockquote>
 D76 – Unicode scalar value: Any Unicode code point except high-surrogate and low-surrogate code points.
 
 <ul>
 <li>As a result of this definition, the set of Unicode scalar values consists of the ranges 0 to D7FF and E000 to 10FFFF, inclusive.</li>
 </ul>
 
 D79 – A Unicode encoding form assigns each Unicode scalar value to a unique code unit sequence.
</blockquote>

Of course, these numbers aren't completely arbitrary due to the mechanism of the surrogate pair encoding laid out in definition D91. Given the bit distribution in Table 3-5, there is just no way to encode a scalar value higher than 10FFFF.

blocks|key|1848650|text|UTF-16编码单元有三种：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1848651|1848652|高代理(U%2BD800到U%2BDBFF)。有1024个这样的。|unordered-list-item|1848653|低代理(U%2BDC00到U%2BDFFF)。在BMP中有1024个these.|1848654|Directly可表示字符。总共有65536-2*1024=63488。|1848655|1848656|有1024×1024+=+1,048,576可以通过代理(“补充字符”U%2B10000到U%2B10FFFF)来表示。将BMP中的63,488个可表示字符相加，得到1,112,064个字符。|1848657|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|P|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|Q|8|@]|9|@]|A|$]]|$1|F|3|G|5|E|7|R|8|@]|9|@]|A|$]]|$1|H|3|I|5|E|7|S|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|T|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

There are three kinds of UTF-16 code units:

<ul>
<li>High surrogates (U+D800 to U+DBFF). There are 1024 of these.</li>
<li>Low surrogates (U+DC00 to U+DFFF). There are 1024 of these.</li>
<li>Directly representable characters in the BMP. There are 65536-2*1024=63488 of these.</li>
</ul>

There are 1024×1024 = 1,048,576 that can be represented through surrogates (the "supplementary characters" U+10000 to U+10FFFF). Add the 63,488 representable characters in the BMP and you get 1,112,064.

Can you calculate that a UTF16 Encoding represents 1,112,064 numbers by permuations/commbinations?

Total number of UTF16 Characters

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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功能1上新10个字符

功能2描述100个字符功能2描述100个字符功能2描述100个字符功能2描述100个字符功能2描述100个字符功能2描述100个字符功能2描述100个字符功能2描述100个字符功能2描述100个字符。

功能2上新100个字符功能2上新100个字符功能2上新100个字符功能2上新100个字符功能2上新100个字符功能2上新100个字符功能2上新100个字符功能2上新100个字符功能2上新100个字符。

功能5描述100个字符功能5描述100个字符功能5描述100个字符功能5描述100个字符功能5描述100个字符功能5描述100个字符

功能5上新100个字符功能5上新100个字符功能5上新100个字符功能5上新100个字符功能5上新100个字符功能5上新100个字符功能5上新100个字符功能5上新100个字符功能5上新100个字符功能5上新100个字符

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你能计算出一个UTF16编码通过排列/组合表示1,112,064个数字吗？

问UTF16字符总数
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回答 5

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