A Turing Machine for the language \(\mathrm{L}=\left\{\mathrm{a}^{\mathrm{n}}…

2022

 A Turing Machine for the language \(\mathrm{L}=\left\{\mathrm{a}^{\mathrm{n}} \mathrm{b}^{\mathrm{m}} \mathrm{c}^{\mathrm{n}} \mathrm{d}^{\mathrm{m}} \mid \mathrm{n} \geq 1, \mathrm{~m} \geq 1\right\}\) is designed. The resultant model is \(M =\)\(\left(\left\{\mathrm{q}_{0}, \mathrm{q}_{1}, \mathrm{q}_{2}, \mathrm{q}_{3}, \mathrm{q}_{4}, \mathrm{q}_{5}, \mathrm{q}_{6}, \mathrm{q}_{7}, \mathrm{q}_{\mathrm{f}}\right\},\{\mathrm{a}, \mathrm{b}, \mathrm{c}, \mathrm{d}\},\left\{\mathrm{a}, \mathrm{b}, \mathrm{c}, \mathrm{d}, \mathrm{X}_{1}, \mathrm{X}_{2}, \mathrm{Y}_{1}, \mathrm{Y}_{2}\right\}, \delta, \mathrm{q}_{0}, \mathrm{~B},\left\{\mathrm{q}_{\mathrm{f}}\right\}\right)\) and part of \(' 𝛿 '\) is given in the transition table. You need to write the following questions based on design of Turing Machine for the given language. Note that, while designing the Turing Machine \(X_1\) and \(X_2\) are used to work with \(′𝑎′𝑠\) and \(′𝑐′𝑠\) and \(Y_1\) and \(Y_2\) are used to handle \(′𝑏′𝑠\) and \(′𝑑′𝑠\) of the given string.

\(\begin{array}{|c|c|c|c|c|c|c|c|c|c|} \hline & \mathrm{a} & \mathrm{b} & \mathrm{c} & \mathrm{d} & \mathrm{X}_{1} & \mathrm{X}_{2} & \mathrm{Y}_{1} & \mathrm{Y}_{2} & \mathrm{~B} \\ \hline \mathrm{q}_{0} & \left(\mathrm{q}_{1}, \mathrm{X}_{1}, \mathrm{R}\right) & & & & \mathrm{M} 2 & & & & \\ \hline \mathrm{q}_{1} & \left(\mathrm{q}_{1}, \mathrm{a}, \mathrm{R}\right) & \left(\mathrm{q}_{1}, \mathrm{~b}, \mathrm{R}\right) & \mathrm{M} 1 & & & \left(\mathrm{q}_{1}, \mathrm{X}_{2}, \mathrm{R}\right) & & & \\ \hline \mathrm{q}_{2} & \left(\mathrm{q}_{2}, \mathrm{a}, \mathrm{L}\right) & \left(\mathrm{q}_{2}, \mathrm{~b}, \mathrm{~L}\right) & & & \left(\mathrm{q}_{2}, \mathrm{X}_{1}, \mathrm{R}\right) & \left(\mathrm{q}_{2}, \mathrm{X}_{2}, \mathrm{~L}\right) & & & \\ \hline \mathrm{q}_{3} & \mathrm{M} 3 & \left(\mathrm{q}_{4}, \mathrm{Y}_{1}, \mathrm{R}\right) & & & & \left(\mathrm{q}_{6} \mathrm{X}_{2}, \mathrm{R}\right) & & & \\ \hline \mathrm{q}_{4} & & \left(\mathrm{q}_{4}, \mathrm{~b}, \mathrm{R}\right) & & \left(\mathrm{q}_{5}, \mathrm{Y}_{2}, \mathrm{~L}\right) & & \mathrm{M} 5 & & \left(\mathrm{q}_{4}, \mathrm{Y}_{2}, \mathrm{R}\right) & \\ \hline \mathrm{q}_{5} & & \left(\mathrm{q}_{5}, \mathrm{~b}, \mathrm{~L}\right) & & & & \left(\mathrm{q}_{5}, \mathrm{X}_{2}, \mathrm{~L}\right) & \mathrm{M} 4 & \left(\mathrm{q}_{5}, \mathrm{Y}_{2}, \mathrm{~L}\right) & \\ \hline \mathrm{q}_{6} & & & & & & \left(\mathrm{q}_{6}, \mathrm{X}_{2}, \mathrm{R}\right) & & \left(\mathrm{q}_{7}, \mathrm{Y}_{2}, \mathrm{R}\right) & \\ \hline \mathrm{q}_{7} & & & & & & & & \left(\mathrm{q}_{7}, \mathrm{Y}_{2}, \mathrm{R}\right) & \left(\mathrm{q}_{6}, \mathrm{~B}, \mathrm{R}\right) \\ \hline \end{array}\)

What is the Move in the cell with number \('M5'\) of the resultant Table?

  1. A.

    \(\left(\mathrm{q}_{4}, \mathrm{X}_{2}, \mathrm{R}\right)\)

  2. B.

    \(\left(\mathrm{q}_{5}, \mathrm{X}_{2}, \mathrm{R}\right)\)

  3. C.

    \(\left(\mathrm{q}_{5}, \mathrm{X}_{2}, \mathrm{~L}\right)\)

  4. D.

    Error Entry

Attempted by 28 students.

Show answer & explanation

Correct answer: A

Move (M5): (q4, X2, R)

Reasoning:

  • Role of state q4: q4 scans right across the b/Y2 region to find the matching d to mark as Y2 and then initiate the leftward return.

  • Encountering X2 while in q4: X2 is a marker for a c that belongs to the a/c matching part. It is not part of the b/d region, so q4 should bypass it rather than change state or move left.

  • Action required: leave the X2 symbol unchanged, remain in q4, and move the head one cell to the right to continue scanning. This corresponds to the transition (q4, X2, R).

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