Characterizations of Pushdown Machines in Terms of Time-Bounded Computers
Journal of the ACM (JACM)
Formal languages and their relation to automata
Formal languages and their relation to automata
On the computational power of pushdown automata
Journal of Computer and System Sciences
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The computational power of 2-way pushodown acceptors with m(=1) additional counters (called mC-PDA) is investigated. It is shown that given any multitape Turing machine M that accepts within time T(n), where n is the input length, one can find a 3C-PDA M' such that M and M' accept the same set of inputs and if M accepts an input w of length n within time T(n), then M' accepts w storing no more than count T(n) in any of the counters. For any such Turing machine, one can also find a 2C-PDA which accepts the same set within count T(n)^2. A number of other results relating the power of 1C-PDA and those of other types of acceptors are also obtained.