What is the -b+ sign in creating locale specific directories in android? [duplicate]

Question

According to android documentation,

To add support for more locales, create additional directories inside res/. Each directory's name should adhere to the following format:

<resource type>-b+<language code>[+<country code>]

For eg.

MyProject/
    res/
       values/
           strings.xml
       values-b+es/
           strings.xml
       mipmap/
           country_flag.png
       mipmap-b+es+ES/
           country_flag.png

Can anybody say why the symbol is like this -b+ ? Just for educational purpose.

Link:
https://developer.android.com/training/basics/supporting-devices/languages.html#CreateDirs

Answer 1

It is a BCP-47 Tag which is added from Java SE 7. It is a IETF Standard to understand the Locale internally and to support the extensions of locale. Thats why android is using values-b+

For more info: https://tools.ietf.org/html/bcp47

https://docs.oracle.com/javase/tutorial/i18n/locale/extensions.html