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字符编码
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ASCII

ISO-8859-1

GB2312

GBK

GB18030

区位码

内码

向下兼容 
    同一个字符在这些方案中总是有相同的编码，后面的标准支持更多的字符.

Unicdoe **Universal Mutliple-Octet Coded Character Set**
    Liteele Endiam
    Big Endian

UCS **Universal Character Set**
    UCS-2
    UCS-4
    BMP Basic Multilingual Plane

UTF **Unicode Transformation Format**
    UTF-8
    UTF-16
    UTF-32
    BOM Byte Order Mark

Unicdoe ==> UTF-8
    1. 0XXXXXXX
    2. 1110XXXX 10XXXXXX 10XXXXXX