What is the -b + sign in creating local specific directories in android?

Question

According to android documentation,

To add support for more locales, create additional directories inside res /. Each directory name must conform to the following format:

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

For instance,

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

Can anyone say why the symbol is like this -b+? For educational purposes only.

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

Answer 1

BCP-47, Java SE 7. IETF, . android -b +

: https://tools.ietf.org/html/bcp47

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