What is an undecidable language?

For an undecidable language, there is no Turing Machine which accepts the language and makes a decision for every input string w (TM can make decision for some input string though). A decision problem P is called “undecidable” if the language L of all yes instances to P is not decidable.

How can you prove that a language is undecidable?

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.

Which of the following are undecidable problem?

Which of the following problems is undecidable? Deciding if a given context-free grammar is ambiguous. Deciding if a given string is generated by a given context-free grammar. Deciding if the language generated by a given context-free grammar is empty.

Which among the following are undecidable theories?

3. Which among the following are undecidable theories? Explanation: Tarski and Mostowski in 1949, established that the first order theory of natural numbers with addition, multiplication, and equality is an undecidable theory.

Are all Undecidable languages recognizable?

Note: Decidable languages are closed under complementation, but recognizable languages are not. – Write-only means (a) symbol on output tape does not affect transitions, and (b) tape head only moves right. Note M need not enumerate strings in order.

Which of the following languages W is undecidable?

L1 is undecidable. According to Rice’s theorem, emptiness problem of Turing machine is undecidable.

Which of the following is are undecidable G is a CFG?

Correct Option: D 1. G is a CFG.

Which of the following statement is false in context of tree terminology?

2. Which of the following statement is false in context of tree terminology? Explanation: A node has atmost one parent, drawn above the node, and zero or more children drawn below. There is one node, one root, that has no parent; this node appears to be at the top of the tree.