Journal of the ACM (JACM)
The Mathematical Theory of Context-Free Languages
The Mathematical Theory of Context-Free Languages
Finite automata and their decision problems
IBM Journal of Research and Development
Abstract families of languages
FOCS '67 Proceedings of the 8th Annual Symposium on Switching and Automata Theory (SWAT 1967)
Hierarchies of memory limited computations
FOCS '65 Proceedings of the 6th Annual Symposium on Switching Circuit Theory and Logical Design (SWCT 1965)
Abstract families of length-preserving processors
Journal of Computer and System Sciences
Journal of Computer and System Sciences
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This paper introduces a new automaton, called a writing pushdown acceptor (abbreviated wpda), and investigates some of its properties. A wpda is essentially a two-way pushdown acceptor that can write on its input tape. A number of results about wpda are established. In particular, it is shown thato(1)Each set accepted by a wpda is accepted by some wpda that halts for all inputs. (2)The family of sets accepted by deterministic wpda forms a Boolean algebra of sets, contains the family of context sensitive languages, and properly contains the family of sets accepted by deterministic two-way pushdown acceptors. (3)The family of sets accepted by (deterministic) wpda is contained in the family of sets accepted by (deterministic) stack acceptors. In the deterministic case, the containment is shown to be proper.