Stack Overflow
Stack Overflow

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

Source

487 questions
9
votes
2 answers

What are all known languages that Turing machines cannot accept?

For example, the language of Turing machines that do not accept their own encoding cannot be accepted by any Turing machine.
Rose Perrone
  • 61,572
  • 58
  • 208
  • 243
8
votes
3 answers

Implementing Control Structures in Brainfuck

For the uninitiated, Brainfuck is a Turing-complete language with only 8 commands, all of which have literal equivalents in C: bf c ---------------------- > ++ptr; < --ptr; + ++*ptr; - --*ptr; . putchar(*ptr); , …
Ryan Tenney
  • 1,812
  • 3
  • 16
  • 29
8
votes
4 answers

How does a non deterministic turing machine work?

I understand they aren't real and they seem to branch computation whenever there are 2 options, instead of picking one. But, for example, if I say this: "Non deterministically guess a bijection p of vertices from Graph G to Graph H" (context here is…
they changed my name
  • 481
  • 2
  • 8
  • 12
7
votes
1 answer

Datalog computational class?

Datalog is not Turing complete. But what is its computational class? Is it equivalent to Finite state machine or Pushdown machine (i.e. context free) ... or is it something in between?
Mustafa
  • 931
  • 1
  • 13
  • 26
7
votes
4 answers

What would the assembly language equivalents of the operations on the original Turing machine be?

If you take the original Turing machine definition as follows: ...an infinite memory capacity obtained in the form of an infinite tape marked out into squares, on each of which a symbol could be printed. At any moment there is …
hawkeye
  • 34,745
  • 30
  • 150
  • 304
7
votes
2 answers

What are the useful limits of Linear Bounded Automata compared to Turing Machines?

There are languages that a Turing machine can handle that an LBA can't, but are there any useful, practical problems that LBAs can't solve but TMs can? An LBA is just a Turing machine with a finite tape, and actual computers have finite storage, so…
Bribles
  • 938
  • 9
  • 23
7
votes
3 answers

Does a turing machine have the concept of 'time'?

I've studied the basic turing machine theory as an undergraduate. I never saw any mention of a timed turing maching. An example: a turing machine that counts the number of seconds passed since it started. Modern computers clearly have the capacity…
Utkarsh Sinha
  • 3,295
  • 4
  • 30
  • 46
6
votes
2 answers

Real world uses of DFA,NFA,PDA and Turing machines

I am now taking a course on Theory of Computation. I can understand the concepts well. I can able to solve the problems. And, when I asked my instructor about the real world application, he told me these concepts will be surely useful and essential…
Muthu Ganapathy Nathan
  • 3,199
  • 16
  • 47
  • 77
6
votes
1 answer

Prove that this language is undecidable

Is the following language L undecidable? L = {M | M is a Turing machine description and there exists an input x of length k such that M halts after at most k steps} I think it is but I couldn't prove it. I tried to think of a reduction from the…
ThP
  • 2,312
  • 4
  • 19
  • 25
6
votes
1 answer

Let T = { | M is a TM that accepts $w^R$ whenever it accepts w}. Show that T is undecidable

Let T = { | M is a TM that accepts wr whenever it accepts w}. Show that T is undecidable. I have two answers to this question - San Diego: 5.9 Let T = { | M is a TM that accepts wr whenever it accepts w }. Assume T is decidable and…
Intuition
  • 137
  • 1
  • 6
6
votes
3 answers

How to tell if a machine is Turing machine equivalent

I found a Wikipedia article of a list of Turing machine equivalents. However, it doesn't tell a method of how to determine whether a given machine is Turing machine equivalent. Do I need to use the definition of a Turing machine to prove it? Could…
Ryan Li
  • 9,020
  • 7
  • 33
  • 62
6
votes
1 answer

A mod B function Turing machine

I'd like to know how can I calculate function A mod B, where A > B and A, B are unary numbers, with a deterministic turing machine with a single tape. Thanks
simone
  • 119
  • 5
  • 16
6
votes
1 answer

Why is E(dfa) a decidable language?

I don't understand why the Turing Machine T, ACCEPTS when no accept state is marked and rejects when an accept state is marked: E(dfa) = {| A is a DFA and L(A) = the empty set(don't have the symbol)} E(dfa) is a decidable language. Proof: A DFA…
h4x0rjax
  • 359
  • 1
  • 6
  • 15
6
votes
1 answer

Multiplication and Module Turing Machine

I need help designing a turing machine that will compute the following f(x,y) = x*y mod 4. how to approach this problem in binary base where $x$ and $y$ have two bits?
Juan
  • 2,073
  • 3
  • 22
  • 37
5
votes
1 answer

Decidability and Recursive Enumerability

Say there exist Turing Machines M1, M2, M3, the languages they recognize being L(M1), L(M2), and L(M3), respectively. The following language L = {(M1, M2, M3) : L(M1), L(M2), and L(M3) are not equal} Is the language decidable? Recursively…
Glen Marek
  • 75
  • 4
1 2
3
…
32 33