User blog comment:LittlePeng9/First order oodle theory/@comment-172.58.107.230-20161109215955/@comment-1605058-20161110125920

The main difference between uncomputable functions and formal languages is that the former are functions while the latter are languages.

Also, BB function is not usually described using formal language, let alone FOST. FOST is not suited well to describing Turing machines.