之前在很多地方都能見到I18N，特別是open source里面。I18N就是Internationalization的縮寫，其原因是I和n之間一共有18個字母。

下面這些地方會需要I18N

• Displaying characters for the users' native languages.
• Inputing characters for the users' native languages.
• Handling files written in popular encodings that are used for the users' native languages.
• Using characters from the users' native languages for file names and other items.
• Printing out characters from the users' native languages.
• Displaying messages by the program in the users' native languages.
• Formatting input and output of numbers, dates, money, etc., in a way that obeys customs of the users' native cultures.
• Classifying and sorting characters, in a way that obey customs of the users' native cultures.
• Using typesetting and hyphenation rules appropriate for the users' native languages.

當然除了I18N還有L10N(localization) 和M17N (multilingualization)，這3個之間有什么區別呢，舉例說明。

L10N支持2種語言，英文和另外一種語言（例如中文）；

I18N支持多種語言，但是同一時間只能是英文和一種選定的語言，例如英文+中文、英文+德文、英文+韓文等等；

M17N可以在同一時間支持多種語言，例如你可以在一個頁面里看到中文、英文、德文和韓文。