Theory of Computation
Finite Automata and Regular Language
Marks 1Marks 2Marks 5
Push Down Automata and Context Free Language
Marks 1Marks 2
Undecidability
Marks 1Marks 2
Recursively Enumerable Language and Turing Machine
Marks 1Marks 2
1
GATE CSE 2006
MCQ (Single Correct Answer)
+2
-0.6
Let $${L_1}$$ be a regular language, $${L_2}$$ be a deterministic context-free language and $${L_3}$$ a recursively enumerable, but not recursive, language. Which one of the following statement is false?
A
$${L_1} \cap {L_2}$$ is deterministic $$CFL$$
B
$${L_3} \cap {L_1}$$ is recursive
C
$${L_1} \cup {L_2}$$ is context-free
D
$${L_1} \cap {L_2} \cap {L_3}$$ is recursively enumerable
2
GATE CSE 2005
MCQ (Single Correct Answer)
+2
-0.6
Let $${L_1}$$ be a recursive language, and Let $${L_2}$$ be a recursively enumerable but not a recursive language. Which one of the following is TRUE?
A
$$\overline {{L_1}} $$ is recursive and $$\overline {{L_2}} $$ is recursively enumerable
B
$$\overline {{L_1}} $$ is recursive and $$\overline {{L_2}} $$ is not recursively enumerable
C
$$\overline {{L_1}} $$ and $$\overline {{L_2}} $$ are recursively enumerable
D
$$\overline {{L_1}} $$ is recursively enumerable and $$\overline {{L_2}} $$ is recursive
3
GATE CSE 2003
MCQ (Single Correct Answer)
+2
-0.6
A single tape Turing Machine $$M$$ has two states $${q_0}$$ and $${q_1}$$, of which $${q_0}$$ is the starting state. The tape alphabet of $$M$$ is $$\left\{ {0,\,\,1,\,\,B} \right\}$$ and its input alphabet is $$\left\{ {0,\,\,1} \right\}$$. The symbol $$B$$ is the blank symbol used to indicate end of an input string. The transition function of $$M$$ is described in the following table. GATE CSE 2003 Theory of Computation - Recursively Enumerable Language and Turing Machine Question 23 English

The table is interpreted as illustrated below. The entry $$\left( {{q_1},1,\,R} \right)$$ in row $${{q_0}}$$ and column $$1$$ signifies that if $$M$$ is in state $${{q_0}}$$ and reads $$1$$ on the current tape square, then it writes $$1$$ on the same tape square, moves its tape head one position to the right and transitions to state $${{q_1}}$$.

Which of the following statements is true about $$M?$$

A
$$M$$ does not halt on any string in $${\left( {0 + 1} \right)^ + }$$
B
$$M$$ does not halt on any string in $${\left( {00 + 1} \right)^ + }$$
C
$$M$$ halts on all string ending in a $$0$$
D
$$M$$ halts on all string ending in $$a$$
4
GATE CSE 2003
MCQ (Single Correct Answer)
+2
-0.6
Define Languages $${L_0}$$ and $${L_1}$$ as follows
$${L_0} = \left\{ { < M,\,w,\,0 > \left| {M\,\,} \right.} \right.$$ halts on $$\left. w \right\}$$
$${L_1} = \left\{ { < M,w,1 > \left| M \right.} \right.$$ does not halts on $$\left. w \right\}$$

Here $$ < M,\,w,\,i > $$ is a triplet, whose first component, $$M$$ is an encoding of a Turing Machine, second component, $$w$$, is a string, and third component, $$t,$$ is a bit.
Let $$L = {L_0} \cup {L_1}.$$ Which of the following is true?

A
$$L$$ is recursively enumerable, but $$\overline L $$ is not
B
$$\overline L $$ is recursively enumerable, but $$L$$ is not
C
Both $$L$$ and $$\overline L $$ are recursive
D
Neither $$L$$ nor $$\overline L $$ is recursive enumerable
GATE CSE Subjects
Theory of Computation
Operating Systems
Algorithms
Digital Logic
Database Management System
Data Structures
Computer Networks
Software Engineering
Compiler Design
Web Technologies
General Aptitude
Discrete Mathematics
Programming Languages
Computer Organization