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 properties of recursive enumerable seta are not decidable? State the halting problem of TMs. What are the conditions for L to be r. The Turing machine is equivalent in computing power to the computtaion computer.

The heads are numbered 1 through k, and move of the TM depends on the state and on the symbol scanned by each head. If anything in the source language matches with this reg exp then it is recognized as an identifier. The most obvious way to do this is to treat the entire nonblank portion of the initial tape as inputand to treat the entire blank portion of the tape when the machine halts as output.


A switching circuit consists of a finite number of gates, each of which can be in any one of the two conditions 0 or 1.

Otherwise the problem is said to be undecidable. It has an infinite tape divided into cells ,each cell holding one symbol.

TOC suggests various abstract models of computation, represented mathematically. What are the possibilities of a TM when processing an input string?


Hence useful productions are: Let L be any CFL. The recursive sets include languages accepted by at least one TM that halts on all inputs.

Turing machine is a simple mathematical model of a computer. A Turing machine can make space on its tape by shifting all nonblank symbols a finite number of cells to the right. What is a Diagonalization language Ld?

Condition i is called the basis step and condition ii is called the inductive step. Language includes empty words also. Consider the ambiguity problem for CFGs.

Thus to model a context free language, a Bahk Automata is used. It can reject the string by entering non-accepting state.


This hierarchy is called as Chomsky Asnwers. The state of the Finite control represents the state ansewrs the second element represent a symbol scanned. If L is an infinite language in ,then there is a finite subset of L in. 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. Pumping lemma is used to check if a language is regular or not. If f i1,i2,………ik is defined for all i1,…. L is recursively enumerable iff satisfies the following properties:.


Thus control unit of a computer is a finite statesystem.

Given any TM M and an input string w, does M halt on w? A regular expression is a string that describes the whole set of strings according to certain syntax rules. Let P n be a ststement about a non negative integer n. Finite Automata is used to model regular expression and cannot be used to represent non regular languages. The regular sets are closed under union, concatenation and Kleene closure.

Wirh examples of recursive languages? Each variable and each terminal of G appears in the derivation of some word in L.