Search results
Results From The WOW.Com Content Network
A diagram of a pushdown automaton. A finite-state machine just looks at the input signal and the current state: it has no stack to work with, and therefore is unable to access previous values of the input. It can only choose a new state, the result of following the transition. A pushdown automaton (PDA) differs from a finite state machine in ...
The two are not equivalent for the deterministic pushdown automaton (although they are for the non-deterministic pushdown automaton). The languages accepted by empty stack are those languages that are accepted by final state and are prefix-free: no word in the language is the prefix of another word in the language. [2] [3]
A two-way deterministic finite automaton (2DFA) is an abstract machine, a generalized version of the deterministic finite automaton (DFA) which can revisit characters already processed. As in a DFA, there are a finite number of states with transitions between them based on the current character, but each transition is also labelled with a value ...
the Z4 (1945) computer by Konrad Zuse had a 2-level stack. [8] [9] the Burroughs large systems architecture (since 1961) the English Electric KDF9 machine. First delivered in 1964, the KDF9 had a 19-level deep pushdown stack of arithmetic registers, and a 17-level deep stack for subroutine return addresses
An embedded pushdown automaton or EPDA is a computational model for parsing languages generated by tree-adjoining grammars (TAGs). It is similar to the context-free grammar-parsing pushdown automaton, but instead of using a plain stack to store symbols, it has a stack of iterated stacks that store symbols, giving TAGs a generative capacity between context-free and context-sensitive grammars ...
A Turing machine is equivalent to a single-stack pushdown automaton (PDA) that has been made more flexible and concise by relaxing the last-in-first-out (LIFO) requirement of its stack. In addition, a Turing machine is also equivalent to a two-stack PDA with standard LIFO semantics, by using one stack to model the tape left of the head and the ...
A nested stack automaton is capable of recognizing an indexed language, [2] and in fact the class of indexed languages is exactly the class of languages accepted by one-way nondeterministic nested stack automata. [1] [3] Nested stack automata should not be confused with embedded pushdown automata, which have less computational power. [citation ...
Stack memory: An automaton may also contain some extra memory in the form of a stack in which symbols can be pushed and popped. This kind of automaton is called a pushdown automaton. Queue memory: An automaton may have memory in the form of a queue. Such a machine is called queue machine and is Turing-complete.