The regular language is recognized by a regular expression or finite state automaton they are ultimately the same thing. A context free language is recognized by a pushdown automaton which is a finite state automaton with a stack. In this respect, these two machines are similar. Likewise, the machines that recognize the context sensitive and unrestricted languages are similar the unrestricted language is recognized by a Turing Machine with an infinite tape the classic machine. A context sensitive language is recognized by a Turing Machine with a tape of a fixed length and is known as a linearbounded automaton. The linearbounded automaton lba is a Turing Machine with a tape of some finite length. The length is a function of the length of the initial input string and a constant for that particular machine. Some definitions of the lba have it that this constant is 1 for all cases and compensating for a shorter tape by having a larger alphabet. A different definition is a Turing Machine where the amount of tape needed can be predicted and is a linear function of the length of the input.

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