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Automata Theory - Lecture 1 DFAs

Published: 2014/09/26

Channel: Antonio Bruto da Costa

Introduction To Finite Automata and Automata Theory

Published: 2013/07/26

Channel: Engineers Minute

Basic Concepts of Automata Theory

Published: 2015/11/22

Channel: kirti Seth

THEORY OF COMPUTATION,OR AUTOMATA THEORY ( INTRODUCTION TO AUTOMATA) LEC - 1

Published: 2016/06/01

Channel: GATE and NET Computer Science video-lec

Lecture 20/65: PDAs: Pushdown Automata

Published: 2015/01/22

Channel: hhp3

Theory of Automata # Introduction And Basics # Lecture1 # Symbol # Alphabet # Language # String

Published: 2016/05/31

Channel: Computer Science Lectures by Ankush Sharma

Deterministic Finite Automata ( DFA ) with (Type 1: Strings ending with)Examples

Published: 2015/06/09

Channel: The BootStrappers

1. INTRODUCTION TO AUTOMATON AND AUTOMATA THEORY

Published: 2014/06/18

Channel: Rishabh Agrawal

TOC | Lecture - 1 | What is Automata? | Computer Logics Instructor

Published: 2016/02/03

Channel: Computer Logics Instructor

Automata Theory : Push Down Automata Tutorial (PDA) Part 1

Published: 2013/02/08

Channel: Debarghya Mukherjee

Introduction to theory of Automata Urdu/Hindi

Published: 2016/08/27

Channel: Sir Malik Shahzaib

Automata Theory - Lecture 5 - 1 - Regular Expressions

Published: 2014/09/26

Channel: Antonio Bruto da Costa

Automata Theory - Lecture 2 NFAs

Published: 2014/09/26

Channel: Antonio Bruto da Costa

CSEDays. Theory 2014. Applications of automata theory in... (Andreas Maletti) day 1

Published: 2014/10/16

Channel: Контур Студент

18 - Automata Theory - Advanced Genetics (175 BPM)

Published: 2014/06/23

Channel: Lunaticalienrecords

Theory Of Computation Lecture 63--Conversion of Finite automata to Regular Expression and vice versa

Published: 2014/06/30

Channel: Gate Lectures by Ravindrababu Ravula

1 Automata : Alphabet, String and Language (Introduction)

Published: 2015/12/29

Channel: saurabhschool

Automata Theory : Context Free Grammar (CFG) to Chomsky Normal Form (CNF) part 2

Published: 2013/02/12

Channel: Debarghya Mukherjee

Theory Of Computation 61 -- Examples of Regular expressions

Published: 2014/06/28

Channel: Gate Lectures by Ravindrababu Ravula

Theory Of Computation lecture 68

Published: 2014/07/21

Channel: Gate Lectures by Ravindrababu Ravula

Automata Theory - Lecture 3 - Closure Properties of Regular Languages

Published: 2014/09/26

Channel: Antonio Bruto da Costa

001 | Theory of Computation or Automata Theory : Introduction to TOC & Basic Concepts

Published: 2015/03/19

Channel: Gate Instructors

Automata Theory - Lecture 6 - Pumping Lemma

Published: 2014/09/26

Channel: Antonio Bruto da Costa

Designing PDA | Pushdown Automata | Theory of Computation(TOC)

Published: 2016/12/17

Channel: Last Minute Tutorials

065 | Examples of Regular Language and Regular Expressions in automata theory (Concepts, Tricks)

Published: 2015/07/17

Channel: Gate Instructors

Theory Of Computation 33,Introduction to NFA

Published: 2013/07/23

Channel: Gate Lectures by Ravindrababu Ravula

L2 Automata Theory, Finite Automatons and DFA, hindi

Published: 2014/02/26

Channel: Mukul World

095 | Regular Expression to Finite Automata DFA NFA | Automata Theory

Published: 2015/07/17

Channel: Gate Instructors

3.1 Finite State Automata, FA,FSA, DFSA

Published: 2016/04/20

Channel: University Of Shamil

012 | Automata Theory : Introduction to Finite Automata and Finite Automata Examples

Published: 2015/03/23

Channel: Gate Instructors

Automata (Theory of Computation) - Lecture 2 (part 1)

Published: 2013/03/30

Channel: Raman Classes

Automata Theory - Poema De Shaka - 190 bpm

Published: 2016/08/16

Channel: Marko

Automata Theory - Lecture 5 - 2 NFA for a Regular Expression

Published: 2014/09/26

Channel: Antonio Bruto da Costa

THEORY OF COMPUTATION - AUTOMATA( THEORY OF COMPUTATION) LEC - 2

Published: 2016/06/01

Channel: GATE and NET Computer Science video-lec

CERIAS Seminar: The role of automata theory in software verification

Published: 2010/12/24

Channel: Christiaan008

066 | Automata Theory : Regular Expression for no pair of consecutive zeros at least one pair

Published: 2015/07/17

Channel: Gate Instructors

Automata Theory Live - Festival Trancedance

Published: 2016/07/06

Channel: Diego Dantas

Automata (Theory of Computation) - Lecture1

Published: 2013/03/30

Channel: Raman Classes

L3 Automata Theory, Extended Transition Function, hindi

Published: 2014/03/07

Channel: Mukul World

Automata Theory vs Lyzergik Brain - Nebulosa - 200 bpm

Published: 2016/08/17

Channel: Marko

Automata (Theory of Computation) - Lecture 2 (Part 2)

Published: 2013/03/30

Channel: Raman Classes

Theory Of Computation lecture 67

Published: 2014/07/21

Channel: Gate Lectures by Ravindrababu Ravula

formal languages and automata theory introduction

Published: 2016/11/16

Channel: Azra Nazir

Topic No 1 CS402 Theory of Automata

Published: 2016/11/22

Channel: VU Academy

Automata Theory -- Hostile Landscapes (175bpm)

Published: 2014/04/24

Channel: Damaru Records

Theory Of Computation 46,Moore Machine and Mealy machine

Published: 2014/05/08

Channel: Gate Lectures by Ravindrababu Ravula

128 | Automata Theory: DFA NFA for Language (na(w) − nb(w)) mod 3 divisible by

Published: 2015/07/18

Channel: Gate Instructors

097 | Conversion of Regular Expression to Finite Automata Examples | Concepts, Tricks & ShortCut

Published: 2015/07/17

Channel: Gate Instructors

016 | Language Acceptance by a NFA (Nondeterministic Finite Automata) : Theory of Computation

Published: 2015/03/23

Channel: Gate Instructors

L1 Automata Theory, Basic Notations of Automata Theory

Published: 2014/02/25

Channel: Mukul World

From Wikipedia, the free encyclopedia

**Automata theory** is the study of abstract machines and automata, as well as the computational problems that can be solved using them. It is a theory in theoretical computer science and discrete mathematics (a subject of study in both mathematics and computer science). The word *automata* (the plural of *automaton*) comes from the Greek word αὐτόματα, which means "self-acting".

The figure at right illustrates a finite-state machine, which belongs to a well-known type of automaton. This automaton consists of states (represented in the figure by circles) and transitions (represented by arrows). As the automaton sees a symbol of input, it makes a transition (or jump) to another state, according to its transition function, which takes the current state and the recent symbol as its inputs.

Automata theory is closely related to formal language theory. An automaton is a finite representation of a formal language that may be an infinite set. Automata are often classified by the class of formal languages they can recognize, typically illustrated by the Chomsky hierarchy which describes the relations between various languages and kinds of formalized logic.

Automata play a major role in theory of computation, compiler construction, artificial intelligence, parsing and formal verification.

Following is an introductory definition of one type of automaton, which attempts to help one grasp the essential concepts involved in automata theory/theories.

An automaton is supposed to *run* on some given sequence of *inputs* in discrete time steps. An automaton gets one input every time step that is picked up from a set of *symbols* or *letters*, which is called an *alphabet*. At any time, the symbols so far fed to the automaton as input, form a finite sequence of symbols, which finite sequences are called *words*. An automaton contains a finite set of *states*. At each instance in time of some run, the automaton is *in* one of its states. At each time step when the automaton reads a symbol, it jumps or transitions to another state that is decided by a function that takes the current state and symbol as parameters. This function is called the *transition function*. The automaton reads the symbols of the input word one after another and transitions from state to state according to the transition function, until the word is read completely. Once the input word has been read, the automaton is said to have stopped and the state at which automaton has stopped is called the final state. Depending on the final state, it's said that the automaton either *accepts* or *rejects* an input word. There is a subset of states of the automaton, which is defined as the set of *accepting states*. If the final state is an accepting state, then the automaton *accepts* the word. Otherwise, the word is *rejected*. The set of all the words accepted by an automaton is called the "language of that automaton". Any subset of the language of an automaton is a *language recognized by that automaton*.

In short, an automaton is a mathematical object that takes a word as input and decides either to accept it or reject it. Since all computational problems are reducible into the accept/reject question on words (all problem instances can be represented in a finite length of symbols)^{[citation needed]}, automata theory plays a crucial role in computational theory.

- Automaton
- A deterministic finite
**automaton**is represented formally by a 5-tuple**(Q,Σ,δ,q**, where:_{0},F)- Q is a finite set of
*states*. - Σ is a finite set of
*symbols*, called the*alphabet*of the automaton. - δ is the
**transition function**, that is, δ: Q × Σ → Q. - q
_{0}is the*start state*, that is, the state of the automaton before any input has been processed, where q_{0}∈ Q. - F is a set of states of Q (i.e. F⊆Q) called
**accept states**.

- Q is a finite set of

- Input word
- An automaton reads a finite string of symbols a
_{1},a_{2},...., a_{n}, where a_{i}∈ Σ, which is called an*input word*. The set of all words is denoted by Σ*. - Run
- A sequence of states q
_{0},q_{1},q_{2},...., q_{n}, where q_{i}∈ Q such that q_{0}is the start state and q_{i}= δ(q_{i-1},a_{i}) for 0 < i ≤ n, is a*run*of the automaton on an input word w = a_{1},a_{2},...., a_{n}∈ Σ*. In other words, at first the automaton is at the start state q_{0}, and then the automaton reads symbols of the input word in sequence. When the automaton reads symbol a_{i}it jumps to state q_{i}= δ(q_{i-1},a_{i}). q_{n}is said to be the*final state*of the run.

- Accepting word
- A word w ∈ Σ* is accepted by the automaton if q
_{n}∈ F.

- Recognized language
- An automaton can recognize a formal language. The language L ⊆ Σ* recognized by an automaton is the set of all the words that are accepted by the automaton.

- Recognizable languages
- The recognizable languages are the set of languages that are recognized by some automaton. For the above definition of automata the recognizable languages are regular languages. For different definitions of automata, the recognizable languages are different.

Automata are defined to study useful machines under mathematical formalism. So, the definition of an automaton is open to variations according to the "real world machine", which we want to model using the automaton. People have studied many variations of automata. The most standard variant, which is described above, is called a deterministic finite automaton. The following are some popular variations in the definition of different components of automata.

- Input

*Finite input*: An automaton that accepts only finite sequence of symbols. The above introductory definition only encompasses finite words.*Infinite input*: An automaton that accepts infinite words (ω-words). Such automata are called*ω-automata*.*Tree word input*: The input may be a*tree of symbols*instead of sequence of symbols. In this case after reading each symbol, the automaton*reads*all the successor symbols in the input tree. It is said that the automaton*makes one copy*of itself for each successor and each such copy starts running on one of the successor symbol from the state according to the transition relation of the automaton. Such an automaton is called a tree automaton.*Infinite tree input*: The two extensions above can be combined, so the automaton reads a tree structure with (in)finite branches. Such an automaton is called an infinite tree automaton

- States

*Finite states*: An automaton that contains only a finite number of states. The above introductory definition describes automata with finite numbers of states.*Infinite states*: An automaton that may not have a finite number of states, or even a countable number of states. For example, the quantum finite automaton or topological automaton has uncountable infinity of states.*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*

- Transition function

*Deterministic*: For a given current state and an input symbol, if an automaton can only jump to one and only one state then it is a*deterministic automaton*.*Nondeterministic*: An automaton that, after reading an input symbol, may jump into any of a number of states, as licensed by its transition relation. Notice that the term transition function is replaced by transition relation: The automaton*non-deterministically*decides to jump into one of the allowed choices. Such automata are called*nondeterministic automata*.*Alternation*: This idea is quite similar to tree automaton, but orthogonal. The automaton may run its*multiple copies*on the*same*next read symbol. Such automata are called*alternating automata*. Acceptance condition must satisfy all runs of such*copies*to accept the input.

- Acceptance condition

*Acceptance of finite words*: Same as described in the informal definition above.*Acceptance of infinite words*: an*omega automaton*cannot have final states, as infinite words never terminate. Rather, acceptance of the word is decided by looking at the infinite sequence of visited states during the run.*Probabilistic acceptance*: An automaton need not strictly accept or reject an input. It may accept the input with some probability between zero and one. For example, quantum finite automaton, geometric automaton and*metric automaton*have probabilistic acceptance.

Different combinations of the above variations produce many classes of automaton.

Automata theory is a subject matter that studies properties of various types of automata. For example, the following questions are studied about a given type of automata.

- Which class of formal languages is recognizable by some type of automata? (Recognizable languages)
- Are certain automata
*closed*under union, intersection, or complementation of formal languages? (Closure properties) - How much is a type of automata expressive in terms of recognizing a class of formal languages? And, their relative expressive power? (Language Hierarchy)

Automata theory also studies if there exist any effective algorithm or not to solve problems similar to the following list.

- Does an automaton accept any input word? (emptiness checking)
- Is it possible to transform a given non-deterministic automaton into deterministic automaton without changing the recognizable language? (Determinization)
- For a given formal language, what is the smallest automaton that recognizes it? (Minimization).

The following is an incomplete list of types of automata.

Automaton | Recognizable language |
---|---|

Nondeterministic/Deterministic Finite state machine (FSM) | regular languages |

Deterministic pushdown automaton (DPDA) | deterministic context-free languages |

Pushdown automaton (PDA) | context-free languages |

Linear bounded automaton (LBA) | context-sensitive languages |

Turing machine | recursively enumerable languages |

Deterministic Büchi automaton | ω-limit languages |

Nondeterministic Büchi automaton | ω-regular languages |

Rabin automaton, Streett automaton, Parity automaton, Muller automaton | ω-regular languages |

Normally automata theory describes the states of abstract machines but there are analog automata or continuous automata or hybrid discrete-continuous automata, which use analog data, continuous time, or both.

The following is an incomplete hierarchy in terms of powers^{[further explanation needed]} of different types of virtual machines.^{[1]}

Automaton |
---|

Deterministic Finite Automaton (DFA) -- Lowest Power (same power) (same power) |

Each model in AT plays important roles in several applied areas. Finite automata are used in text processing, compilers, and hardware design. Context-free grammar (CFGs) are used in programming languages and artificial intelligence. Originally, CFGs were used in the study of the human languages. Cellular automata are used in the field of biology, the most common example being John Conway's Game of Life. Some other examples which could be explained using automata theory in biology include mollusk and pine cones growth and pigmentation patterns. Going further, a theory suggesting that the whole universe is computed by some sort of a discrete automaton, is advocated by some scientists. The idea originated in the work of Konrad Zuse, and was popularized in America by Edward Fredkin.

Automata simulators are pedagogical tools used to teach, learn and research automata theory. An automata simulator takes as input the description of an automaton and then simulates its working for an arbitrary input string. The description of the automaton can be entered in several ways. An automaton can be defined in a symbolic language or its specification may be entered in a predesigned form or its transition diagram may be drawn by clicking and dragging the mouse. Well known automata simulators include Turing’s World, JFLAP, VAS, TAGS and SimStudio.^{[2]}

One can define several distinct categories of automata^{[3]} following the automata classification into different types described in the previous section. The mathematical category of deterministic automata, sequential machines or *sequential automata*, and Turing machines with automata homomorphisms defining the arrows between automata is a Cartesian closed category,^{[4]}^{[5]} it has both categorical limits and colimits. An automata homomorphism maps a quintuple of an automaton *A*_{i} onto the quintuple of another automaton *A*_{j}.^{[6]} Automata homomorphisms can also be considered as *automata transformations* or as semigroup homomorphisms, when the state space, * S*, of the automaton is defined as a semigroup

- Categories of variable automata

One could also define a *variable automaton*, in the sense of Norbert Wiener in his book on *The Human Use of Human Beings* *via* the endomorphisms . Then, one can show that such variable automata homomorphisms form a mathematical group. In the case of non-deterministic, or other complex kinds of automata, the latter set of endomorphisms may become, however, a *variable automaton groupoid*. Therefore, in the most general case, categories of variable automata of any kind are categories of groupoids or groupoid categories. Moreover, the category of reversible automata is then a 2-category, and also a subcategory of the 2-category of groupoids, or the groupoid category.

**^**Yan, Song Y. (1998).*An Introduction to Formal Languages and Machine Computation*. Singapore: World Scientific Publishing Co. Pte. Ltd. pp. 155–156.**^**Chakraborty, P., Saxena, P. C., Katti, C. P. 2011. Fifty Years of Automata Simulation: A Review.*ACM Inroads*,**2**(4):59–70. http://dl.acm.org/citation.cfm?id=2038893&dl=ACM&coll=DL&CFID=65021406&CFTOKEN=86634854**^**Jirí Adámek and Vera Trnková. 1990.*Automata and Algebras in Categories*. Kluwer Academic Publishers:Dordrecht and Prague**^**S. Mac Lane, Categories for the Working Mathematician, Springer, New York (1971)**^**Cartesian closed category Archived November 16, 2011, at the Wayback Machine.**^**The Category of Automata Archived September 15, 2011, at the Wayback Machine.**^**http://www.csee.wvu.edu/~jworthing/asl2010.pdf James Worthington.2010.Determinizing, Forgetting, and Automata in Monoidal Categories. ASL North American Annual Meeting,March 17, 2010**^**Aguiar, M. and Mahajan, S.2010.*"Monoidal Functors, Species, and Hopf Algebras"*.**^**Meseguer, J., Montanari, U.: 1990 Petri nets are monoids.*Information and Computation***88**:105–155

- John E. Hopcroft, Rajeev Motwani, Jeffrey D. Ullman (2000).
*Introduction to Automata Theory, Languages, and Computation (2nd Edition)*. Pearson Education. ISBN 0-201-44124-1. - Michael Sipser (1997).
*Introduction to the Theory of Computation*. PWS Publishing. ISBN 0-534-94728-X. Part One: Automata and Languages, chapters 1–2, pp. 29–122. Section 4.1: Decidable Languages, pp. 152–159. Section 5.1: Undecidable Problems from Language Theory, pp. 172–183. - Elaine Rich (2008).
*Automata, Computability and Complexity: Theory and Applications*. Pearson. ISBN 0-13-228806-0. - Salomaa, Arto (1985).
*Computation and automata*. Encyclopedia of Mathematics and Its Applications.**25**. Cambridge University Press. ISBN 0-521-30245-5. Zbl 0565.68046. - Anderson, James A. (2006).
*Automata theory with modern applications*. With contributions by Tom Head. Cambridge: Cambridge University Press. ISBN 0-521-61324-8. Zbl 1127.68049. - Conway, J.H. (1971).
*Regular algebra and finite machines*. Chapman and Hall Mathematics Series. London: Chapman & Hall. Zbl 0231.94041. - Sakarovitch, Jacques (2009).
*Elements of automata theory*. Translated from the French by Reuben Thomas. Cambridge University Press. ISBN 978-0-521-84425-3. Zbl 1188.68177. - James P. Schmeiser, David T. Barnard (1995).
*Producing a top-down parse order with bottom-up parsing*. Elsevier North-Holland. - Igor Aleksander, F.Keith Hanna (1975).
*Automata Theory : An Engineering Approach*. New York: Crane Russak. ISBN 0-8448-0657-9. - Marvin Minsky (1967).
*Computation : Finite and infinite machines*. Princeton, N.J.: Prentice Hall.

- Visual Automata Simulator, A tool for simulating, visualizing and transforming finite state automata and Turing Machines, by Jean Bovet
- JFLAP
- dk.brics.automaton
- libfa

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