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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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Turing machine given the following inputs: 1010

I am studying for exams and I have no idea on how to come up with a turing machine state table given the following inputs 111101 (State, Input/Read, Write, Move, Next State). Any idea where I can get simplified tutorials on turing machines.
user3225573
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How to shift data in turing machine?

While converting multitape turing machine into an equivalent singletape turing machine we have to shift the data and insert a blank to it. e.g : Multitape = [1,2,3,4] [5,6,7,8] [9,10,11,12] Equivalent singletape =…
user3778989
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Prove whether this language is decidable or undecidable

So I am reviewing my notes for this problem, and I cant seem to understand how this problem works. Say we have M, and M accepts an input that makes it visit every non-halting state. I convinced myself that this problem is decidable, but I am having…
user4077377
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What does a Turing machine do when it reaches the end of it's input?

If a Turing Machine has an input tape of 01011, for example, what happens if you reach the end of that sequence without reaching any resolution within the Turing Machine?
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Cannot create algorithm for decidable language

L2 = { : M is a TM and there exists an input string w such that M halts within 10 steps on input w} Hi. I am creating an algorithm to show above L2 is decidable. And the hint is given as following: To show L2 is decidable, test given TM M on…
Ryu Hoshi
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What's the difference between dovetailing and concurrency?

I came across the definiton of Dovetailing which I had not heard of before and first thing that came to my mind was Concurrency. However, I couldn't find any post relating these two concepts. I also read this. If I'm not mistaken, dovetailing is…
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A language that can be recognised by a TM but cannot be decided by a TM?

Can a language which can be recognised by a TM but cannot be decided by a TM? example of a language which can be recognised by a TM but cannot be decided by a TM Would the answer be: TM={ M is a TM that accepts input string w} Could I be…
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Dutch Flag on a Turing machine with one ribbon with a n.log(n) complexity?

The Dutch national problem is this problem : I have a sequence of characters x^k (k >= 3) My goal is to transform this sentence into a dutch flag, that is to say : xxx gives RWB xxxx gives RWBB xxxxx gives RWWBB xxxxxx gives RRWWBB ... with R <= W…
Koala EnChocolat
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Theory of Computation turing machine

What are the implications of a non-blank character being over-written by a Turing machine M for the given input variable 'x'? Intention of the question: I am trying to answer how the halting problem can be made decidable provided we have a TM which…
Rohit Mittal
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Two Different Grammars Over One Set of Outputs

Can you give me 2 different grammars which outputs the same set of words? Illustration: Given a grammar A and B over the alphabet {0,1}, if grammar A can produce the word 0101001, grammar B could as well. If grammar B can produce 0101111 then…
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Turing Machine to Generate Fibonacchi series

Is it possible (as shown in following image), for given number of consecutive 1's in turing machine's tape, to generate fibonacchi series of given pattern: (Following image represents fibonacchi series of length 5, & consider '0' to represent first…
ShubhamNext
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Turing Completeness in the real world

Real programs can solve problems given enough time and space. For every problem instance of known size, there is fixed upper bound on the amount of space which is consumed. Are there problems that cannot be solved (i.e. functions which cannot be…
Matei
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Describing the action of a Turing Machine

I'm trying to answer the third part to the following question: I have drawn the following state diagram: According to the solution, the machine "adds 1 to a binary number with its least significant bit in the leftmost position on the tape". I…
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Polynomial Time Algorithm for directed graph with path from 's' to 't'

My textbook for theory of computation has an example for explaining polynomial time algorithms: PATH = {[G,s,t]|G is a directed graph that has a directed path from s to t}. A polynomial time algorithm M for PATH operates as follows. M = “On input…
Nathan Miranda
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Turing Degree and Local Contest Questions?

I ran into a olympiad question on Practical Computer Knowledge. For A ⊆ ℕ we have a = degT(A) = {B | B ≡T A} and D = {degT(A) | A ⊆ ℕ}. For (D, ≤) that has A ≤T B iff a ≤ b. Which of the following is false: (D,≤) is a distributive lattice (D,≤)‌…
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