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Problem A126.doc
Problem 26
Describe two different Turing machines, M and N, where, when started on
any input, M outputs (N( and N outputs (M(.
Automata and Computability - Let C be a language. Prove that C turing-recognizable if a decidable language D exists such that C = {x | y (x,y D)}.
Automata and Computability - Show that the collection of Turing-recognizable languages is closed under the operations of
a. union.
b. concatenation.
c. star.
d. intersection
Automata and Computability - A Turing machine with doubly infinite tape is similar to an ordinary Turing machine except that its tape is infinite to the left as well as to the right. The tape is initially filled with blanks exce ...
Automata and Computability - Consider the problem of testing whether a Turing machine M on an input w ever attempts to move its head left when its head is on the left-most tape cell. Formulate this problem as a language and show ...