Theory of computation (TOC) (CS) (CS) (CS53) ( CS) Question Bank 1 (old) – View Question Bank 2 (old) – View / Download Question bank. Anna University Department of computer science engg Fifth Semester CS theory of computation (Regulation ) Semester: 5. Third Year CSE(Sem:V) 2 marks Questions and Answers NFA can be used in theory of computation because they are more flexible and easier to use than.

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What are the applications of Context free languages. The TM can then return to the vacated cells and prints symbols. Language includes empty words also.

Ansers on the state and symbol scannedthe device changes state wth, prints a new symbol and moves its tapehead in one of the 2k directions, either positively or negatively ,along one of the k-axes. Thus reg exp identifies token in a language. FA accepts a string x if the sequence of transitions corresponding to the symbols of x leads from the start state to accepting state. The move dependent on the input symbol a scanned is:.

Let P n be a ststement about a non negative integer n. The universal language consists of a set of binary strings in the form of. Find CFG with no useless symbols equivalent to: CFL are not closed under intersectioncomplementation.

All combinations with the pattern The components of FA model are Input tape, Read control and finite control. A lexical analyzer scans the symbols of a program to locate strings corresponding to identifiers, constants etc, and it has to computahion limited amount of information.

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Simplified the definition of programming languages. Checking off symbols is useful method when a TM recognizes a language with repeated strings and also to compare the length of substrings. Turing machine is a simple mathematical model of a computer.

The tokens of the programming language can be expressed using regular expressions. Then L is not a regular language. All common arithmetic functions on integers such as multiplicationn! This hierarchy is called as Chomsky Hierarchy.

A multi-tape Turing machine consists of a finite control with k-tape heads and ktapes ; each tape is infinite in both directions. Grammar or regular expression Generative approach Automaton Recognition approach.

A problem whose language is recursive is said to be decidable. The lexical analyzer scans the input program and separates the tokens. In one move, the heads may each move independently left or right or remain stationary. Give examples of recursive languages? The heads are numbered 1 through k, and move of the TM depends on the state and on the symbol scanned by each head. When a recursively enumerable language is said to be recursive?

Otherwise the problem is said to be undecidable.


Each variable and each terminal of G appears in the derivation of some word in L. A regular expression is a string that describes the whole set of strings according to certain syntax rules. Given any TM M and an input string w, does M halt on w?

The set of finite languages in is enumaerable. The most obvious way to do this is to treat the entire nonblank portion of the initial tape as inputand to treat questiom entire blank portion of the tape when the machine halts as output. The device has a finite controlbut the tape consists of a k-dimensional array of cells infinite in all 2k directions, for some fixed k.


State the halting problem of TMs. F is the set of final states. M is a DFSM that. The regular expression R is given as: In one move ,TM depending upon the symbol scanned by the tape head and state of the finite control:. A function f i1,…ik computed by a Turing machine is called a partial recursive function.

Apart from the halt statea given TM is total. What are the components of Finite automaton model? What is canonical ordering? The left move is: Turing machine can change symbols on witu tapewhereas the FA cannot change symbols on tape.


What are the applications of Compputation expressions and Finite automata Lexical analyzers and Text editors are two applications. What are the concepts used in UTMs?

The languages that is accepted by TM is said to be recursively enumerable r. Transition diagram is a directed graph in which the vertices of the graph correspond to the states of FA.

It can reject the string by entering non-accepting state. L is recursively enumerable iff satisfies the following properties:. P n-1 is called the induction hypothesis. The recursive sets include languages accepted by at least one TM that halts on all inputs.

Thus control unit of a computer is a finite statesystem. Find the language generated by: