# Is Halting problem only applicable to infinite languages

Is the halting problem, only applicable for infinite languages?

I assume that if the language is finite, then we can search over all words?

• What do you mean by "applicable"? The halting problem makes sense for any language. – Yuval Filmus Jun 19 at 14:31
• @YuvalFilmus I meant that if the language was finite, then you could scan all possible solutions? For example, if L has one element, then we can know if it will halt by checking if the input is equal to the one element in L? – WeCanBeFriends Jun 19 at 14:40
• The halting problem accepts as input a (description of) a Turing machine $M$ and an input $x$, and the goal is to decide whether $M$ halts on $x$. If you fix $M$ then it's no longer the halting problem. – Yuval Filmus Jun 19 at 14:47
• @YuvalFilmus What do you mean by "Fix M" ? To re-say what I think you said: The Halting problem is a problem that takes in any arbitrary Turing Machine and input. If this is correct, then if the M arbitrarily chosen is defined over a finite language, then can we not just check the set? – WeCanBeFriends Jun 19 at 14:52
• The halting problem accepts as an input a Turing machine $M$ and an input $x$, and the goal is to decide whether $M$ halts on $x$. Another formulation fixes $x$: the input is just a Turing machine $M$, and the goal is to decide whether $M$ halts on the empty input (say). Anything else is not the halting problem. You mention "the language", but I'm not sure how it fits in this picture. – Yuval Filmus Jun 19 at 14:53