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Automata theory and Computability - Jun 18
Computer Science (Semester 5)
Total marks: 80
Total time: 3 Hours
INSTRUCTIONS
(1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Draw neat diagrams wherever necessary.

Also write transition table for DFSM.
OR
Module - 2
i) $\mathrm{L}=\left\{\mathrm{a}^{*} \mathrm{b}^{\mathrm{m}} | \mathrm{m}+\mathrm{n} \text { is even }\right\}$
ii) $\mathrm{L}=\left\{\mathrm{a}^{*} \mathrm{b}^{\prime \prime} | \mathrm{m} \geq 1, \mathrm{n} \geq 1, \mathrm{nm} \geq 3\right\}$
iii) $\mathrm{L}=\left\{\mathrm{w} :|\mathrm{w}| \mathrm{mod} 3=0 \text { where we }(\mathrm{a}, \mathrm{b})^{*}\right\}$
OR
Module - 3
$S \rightarrow a B | b A$
$A \rightarrow a S |$ bAA $|$ a $B \rightarrow b S|a B B| b$ \lt/div\gt \ltspan class='paper-ques-marks'\gt(8 marks)\lt/span\gt \ltspan class='paper-page-id'\gt00\lt/span\gt \lt/div\gt **OR** \ltDIV class='paper-question'\gt \ltDIV class='paper-ques-desc'\gt \ltb\gt6.a.\lt/b\gt Define PDA (Push Down Automata). Obtain a PDA to accept the language where WR is reverse of W by a final state. \lt/div\gt \ltspan class='paper-ques-marks'\gt(8 marks)\lt/span\gt \ltspan class='paper-page-id'\gt00\lt/span\gt \lt/div\gt \ltDIV class='paper-question'\gt \ltDIV class='paper-ques-desc'\gt \ltb\gt6.b.\lt/b\gt For the grammar \lt/div\gt \ltspan class='paper-ques-marks'\gt(4 marks)\lt/span\gt \ltspan class='paper-page-id'\gt00\lt/span\gt \lt/div\gt \ltDIV class='paper-question'\gt \ltDIV class='paper-ques-desc'\gt \ltb\gt6.c.\lt/b\gt Obtain a CFG for the PDA shown below: \lt/div\gt \ltspan class='paper-ques-marks'\gt(5 marks)\lt/span\gt \ltspan class='paper-page-id'\gt00\lt/span\gt \lt/div\gt **Module - 4** \ltDIV class='paper-question'\gt \ltDIV class='paper-ques-desc'\gt \ltb\gt7.a.\lt/b\gt Consider the grammar $\mathrm{S} \rightarrow 0 \mathrm{A} | 1 \mathrm{B}$ $\wedge \rightarrow 0 \mathrm{AA}|1 \mathrm{S}| 1$ $\mathrm{B} \rightarrow 1 \mathrm{BB}|0 \mathrm{S}| 0$ Obtain the grammar in CNF. \lt/div\gt \ltspan class='paper-ques-marks'\gt(8 marks)\lt/span\gt \ltspan class='paper-page-id'\gt00\lt/span\gt \lt/div\gt \ltDIV class='paper-question'\gt \ltDIV class='paper-ques-desc'\gt \ltb\gt7.b.\lt/b\gt Show that $\mathrm{L}=\left{\mathrm{a}^{} \mathrm{b}^{} \mathrm{c}^{n} | \mathrm{n} \geq 0\right}$ is not context free. \lt/div\gt \ltspan class='paper-ques-marks'\gt(8 marks)\lt/span\gt \ltspan class='paper-page-id'\gt00\lt/span\gt \lt/div\gt **OR** \ltDIV class='paper-question'\gt \ltDIV class='paper-ques-desc'\gt \ltb\gt8.a.\lt/b\gt With a neat diagram, explain the working of a basic Turing machine. \lt/div\gt \ltspan class='paper-ques-marks'\gt(4 marks)\lt/span\gt \ltspan class='paper-page-id'\gt00\lt/span\gt \lt/div\gt \ltDIV class='paper-question'\gt \ltDIV class='paper-ques-desc'\gt \ltb\gt8.b.\lt/b\gt Obtain a Turing machine to accept the language \lt/div\gt \ltspan class='paper-ques-marks'\gt(8 marks)\lt/span\gt \ltspan class='paper-page-id'\gt00\lt/span\gt \lt/div\gt \ltDIV class='paper-question'\gt \ltDIV class='paper-ques-desc'\gt \ltb\gt8.c.\lt/b\gt Briefly explain the techniques for TM construction. \lt/div\gt \ltspan class='paper-ques-marks'\gt(4 marks)\lt/span\gt \ltspan class='paper-page-id'\gt00\lt/span\gt \lt/div\gt **Module - 5** \ltDIV class='paper-question'\gt \ltDIV class='paper-ques-desc'\gt \ltb\gt9.a.\lt/b\gt Obtain a Turing machine to recognize the language \lt/div\gt \ltspan class='paper-ques-marks'\gt(8 marks)\lt/span\gt \ltspan class='paper-page-id'\gt00\lt/span\gt \lt/div\gt \ltDIV class='paper-question'\gt \ltDIV class='paper-ques-desc'\gt \ltb\gt9.b.\lt/b\gt Prove that $\mathrm{HALT}_{\mathrm{rm}}={(\mathrm{M}, \mathrm{W}) |$ the Turing machine M halts on input W} is undecidable.
OR

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