What does b mean, and what is the syntax of b + sr + Latn?

Question

By default, Android is always displayed in Serbian in Cyrillic, but from 7.0 users can choose between Cyrillic and Latin script. Applications (mainly from Google) intelligently place Cyrillic strings in srand Latin strings in b+sr+Latn. However, b+sr+Latnit is very different from the usual dash agreement (for example, sr-rRS-port).

What does b mean? What is the syntax, and what else can I point out with this?

Answer 1

This is a BCP 47 language tag. It starts with the letter b and is accompanied by a language, script, region, and variant.
BCP 47 Documentation

b+sr+Latn script.
b+sr+Latn+RS , script.

:
b+az+Latn - script
b+az+Cyrl - script
b+az+Arab - script

:
b+ja+Hrkt -
b+ru+Latn - script
b+hu+Hung - script
b+en+Cyrl+US - script
b+hy+Piqd+DE - script
( )

. :
ISO 639-3
ISO 15924 script
ISO 3166-1 -2