Recognizing Automaton

A recognizing automaton is an abstract computer that reads symbols from an input tape. It has a finite control (computer program) and an auxiliary memory.

The recognizer answers ``Yes'' or ``No'' to the question ``Is the input string a member of the language?''

The kinds of languages that can be recognized depend on the amount of auxiliary memory the automaton has (finite, pushdown stack, tape whose size is a linear multiple of input length, infinite tape).