Lifehacks

# What is meant by a Decidable problem?

## What is meant by a Decidable problem?

(definition) Definition: A decision problem that can be solved by an algorithm that halts on all inputs in a finite number of steps. The associated language is called a decidable language. Also known as totally decidable problem, algorithmically solvable, recursively solvable.

## What is decidable problem give an example?

Examples. A classic example of a decidable decision problem is the set of prime numbers. It is possible to effectively decide whether a given natural number is prime by testing every possible nontrivial factor.

What is decidable computer science?

decidable (comparative more decidable, superlative most decidable) capable of being decided. (computer science) describing a set for which there exists an algorithm that will determine whether any element is or is not within the set in a finite amount of time.

### What is undecidable problem in computer science?

There are some problems that a computer can never solve, even the world’s most powerful computer with infinite time: the undecidable problems. An undecidable problem is one that should give a “yes” or “no” answer, but yet no algorithm exists that can answer correctly on all inputs.

### Which one of the following is decidable problem?

1) This is a variation of Turing Machine Halting problem and it is undecidable. 2)CFL are not closed under complement so it is undecidable. 3) Complement of Regular languages is also regular. 4) Recursvie language are closed under complement,so it is decidable.

Is the halting problem decidable?

The halting problem is theoretically decidable for linear bounded automata (LBAs) or deterministic machines with finite memory. A machine with finite memory has a finite number of configurations, and thus any deterministic program on it must eventually either halt or repeat a previous configuration: …

#### Why is fol Undecidable?

If ~B is arrived at, then A implies ~B in every interpretation. First order logic is undecidable, which means (again, I think) that given a set of sentences A and a sentence B, there is no procedure for determining whether A implies B (i.e. it’s not the case that A are true and B is false) in all interpretations.

#### What is the difference between PDA and TM?

Answer. A PDA can only access the top of its stack, whereas a TM can access any position on an infinite tape. An automaton with access to two stacks rather than just one can simulate a TM and thus has equivalent computational power.

How do you show an undecidable problem?

Your language L is indeed undecidable. This can be shown by reducing the halting problem to L: For the halting problem instance (N, y), create a new machine M for the L problem. On input x, M simulates (N, y) for length(x) steps. If the simulation halted within that number of steps, then M halts.

## What types of problems are undecidable?

In computability theory, an undecidable problem is a type of computational problem that requires a yes/no answer, but where there cannot possibly be any computer program that always gives the correct answer; that is, any possible program would sometimes give the wrong answer or run forever without giving any answer.

## What do we call a problem if it has an algorithm to answer it?

Discussion Forum

Que. If a problem has an algorithm to answer it, we call it _________
b. solved
c. recognizable
d. none of the mentioned

Which of the following problems are undecidable Gate 1989?

arrow_back GATE CSE 1989 | Question: 3-iii. Which of the following problems are undecidable? Membership problem in context-free languages. Whether a given context-free language is regular.

### Which is the best definition of a decidable problem?

Definition:A decision problemthat can be solved by an algorithmthat halts on all inputs in a finite number of steps. The associated language is called a decidable language. Also known astotally decidable problem, algorithmically solvable, recursively solvable.

### Is the halting problem a decidable or undecidable problem?

This means that there exists an algorithm that halts eventually when the answer is yes but may run for ever if the answer is no. Partially decidable problems and any other problems that are not decidable are called undecidable. In computability theory, the halting problem is a decision problem which can be stated as follows:

When is a decision problem called semi-decidable or effectively solvable?

A decision problem A is called decidable or effectively solvable if A is a recursive set. A problem is called partially decidable, semi-decidable, solvable, or provable if A is a recursively enumerable set.

#### Are there any problems that are never decidable?

By checking the production rules of the CFL we can easily state whether the language generates any strings or not. The problems for which we canâ€™t construct an algorithm that can answer the problem correctly in finite time are termed as Undecidable Problems. These problems may be partially decidable but they will never be decidable.