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Questions tagged [turing-machines]

A Turing machine is an idealized model of computation consisting of a finite-state control, an infinite tape holding information, and a read head positioned somewhere over the tape. Turing machines are used in computability theory to reason about the limits of computation, to provide a formal definition for an algorithm, and to provide formal models for nondeterminism.

Wiki

A Turing machine is a device that manipulates symbols on a strip of tape according to a table of rules. Despite its simplicity, a Turing machine can be adapted to simulate the logic of any computer algorithm, and is particularly useful in explaining the functions of a CPU inside a computer.

Turing machines are not physical objects but mathematical ones. A Turing machine is a kind of state machine. At any time the machine is in any one of a finite number of states. Instructions for a Turing machine consist in specified conditions under which the machine will transition between one state and another.

The tape is used to store data. In addition, it can also store a series of transitions (a small programs) and thus, the head can run sub-programs. By analogy with modern computers, the tape is the memory and the head is the microprocessor.

Tag usage

The tag can be used for programming related problems in implementing features of a turing machine. The tag can also be used for algorithmic problems related to turing machine. Try to avoid theoretical and research based questions on Stack Overflow.

Please note https://cstheory.stackexchange.com is another stack exchange website which you can use to ask theoretical and conceptual problems with tag

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Does this proof really prove undecidability of halting?

I want to ask a couple questions about the following proof. The proof originally came from a textbook and then a question on stackoverflow below. How does this proof, that the halting problem‍​ is undecidable, work? Question 1: Does the proof below…
Josh
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turing computable function

Here are few True False questions: Somebody please answer these: Let F(0) = 1, and let F(n) = 2^F(n-1) for n>0. Then Is F Turing-Computable? No language which has an ambiguous context-free grammar can be accepted by a DPDA. Is this true ? If not…
Niraj Rana
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L = {T | T is a turing machine that recognizes {00, 01}} Prove L is undecidable

L = { | T is a turing machine that recognizes {00, 01}} Prove L is undecidable. I am really having difficulties even understanding the reduction to use here. I'm not asking for free lunch, just a push in the right direction.
user1405177
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Designing a Turing-machine which halts

I am asked to design a turing-machine (the oldschool way using states and an explicit delta-function). Requirement is: Input is epsilon (infinite number of "blank" symbols) on which the TM should halt, the used alphabet is {B, 0, 1} (with B being…
LDericher
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On-line simulation of a two-head tape Turing machine using single-head tape(s)

I have a question and I haven't been able to figure out the answer yet. I need to do the on-line simulation of a two-head tape Turing machine using single-head tape(s). I've found some online articles for the fact that one single-head tape doesn't…
user1667199
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Where can I find sample automata and turing machines?

I'm studying for an automata test on a course that's heavily based on jflap. Trouble is we don't have much documentation and the sample automata that I've found on jlap like this and this, are insufficient to prepare for the upcoming test. Where…
andandandand
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Programming languages more than turing complete?

I read about turing complete from this answer. From what I understood, for a programming language to be turing complete it should be able to compute everything a turing machine can. Lets consider Python. I know for a fact that Python is turing…
Mike
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What is the quickest algorithm to merge input symbols and remove blanks in a turing machine

I am looking to find an algorithm that would let me while starting at the right most of an input string containing blanks in between, merge input symbols so that there are no blanks. For example, 0 _ 0 _ 0 _ into 000. I am aware of methods shown in…
Kieran Anderson
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L={aʲbᵏaˡ | l = j * k} Context free? Recursive?

I have to classify the language L={aˆjbˆkaˆl | l = j * k}. I applied the pumping lemma for CFL and think that it is not context free. However, to prove that it is in fact recursive or recursively enumerable, would I have to be able to construct a…
nTn
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How to build special turing machine

Good day. I have a question. Many people are familiar with the Turing machine. The following task arose, which I can’t solve for a long time: there is an alphabet consisting of the letters "X", "Y" "Z", if the number of letters "Z" in the word is…
nyar
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Turing machines and decidability

It is known that there are decidable problems, semi-decidable problems, and undecidable problems. A language that is accepted by a TM (Turing Machine) is a r.e. set (recursively enumerable), and, in some cases, a recursive set as well. An example of…
jbushi
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Show that the class of decidable languages is closed under the operations of: Complementation, Concatenation, and Intersection

I understand that the problem is asking for a proof for the specified Turing machine. My issue derives from not being able to understand what type of structure this problem is proposing, as indicated below: We say that a class C of languages is…
Totsuka Blade
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How to decide if a language is In R or RE or CoRE

I have these three languages I don't know how to decide whether the language is in R or RE or coRE L1={| epsilon belongs to L(M)} L2={|M doesn't accept any prefix of w} L3={|there exists w where M accepts all the prefixes of w}
S K
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Mutli-track Turing Machines

I'm doing my homework, and i have a problem with multi-tape (multi-track) Turing Machine: We have multi-tape Turing Machine, which always before moving a head left, writes a blank symbol. Does this machine recognise the same class of languages as…
Janek Podwysocki
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Turing machine states design

I want to design a Turing machine that accepts at most 3 0s. Now, I have designed one, which goes to accept state overtime it sees 1, 2 and 3 0s and rejects any further 0s. I wanted to know if it is okay for TM to go to accepting state from 3…
user9179677
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