Regular Languages

In this chapter, some selected topics of regular languages are involved. The contents of the chapter can be divided into two parts. In Sects. 3.1–3.3, a brief introduction to the theory of regular languages, including the automata theory of regular languages and the equivalence of the three concepts of languages: regularity, recognizability and rationality, are given. This part is classical and elementary and can be found in many books on the theory of formal languages and automata. The second part (Sects. 3.4–3.5) introduces some special topics of regular languages such as some decompositions of regular languages and restricted Burnside problem of semigroups (which is related to regular languages).