Some characterizations of multihead finite automata

Abstract

We give characterizations of multihead two-way finite automata in terms of multihead reversal-bounded pushdown automata and restricted checking stack automata. In particular, we show that a language is accepted by a 2k-head two-way finite automaton if and only if it is accepted by a k-head two-way pushdown automaton which makes one reversal on its stack. We also show that a 2-head two-way deterministic finite automaton is equivalent to a simple type of two-way deterministic checking stack automaton. This is in contrast to a previously known result which shows that simple two-way nondeterministic checking stack automata are equivalent to nondeterministic linear bounded automata.