Two-dimensional automata with rotated inputs

Abstract This paper introduces a new type of automata on a two-dimensional tape, which decides acceptance or rejection of an input tape x by scanning the tape x from various sides by various automata. The accepting power of such an automaton is investigated. This paper mainly concentrates on investigating the accepting power of two-dimensional automata which consist of four parallel/sequential array automata, say M 1 , M 2 , M 3 , and M 4 , and which accept an input tape x if and only if x , x R , ( x R ) R , and (( x R ) R ) R are accepted by M 1 , M 2 , M 3 , and M 4 , respectively, where for any tape y , y R is the tape obtained by rotating y clockwise 90°.