
So let's construct a table like this. In the first column, we'll consider different programs.

And I'm just going to label them p1 for the first program, p2 for the second program, and so on and so on.

In the second column we'll then consider different cases of what halt can say with respect to that program,

when considering what happens if the program is run on itself.

So for example, we might say that for P1, halt might say yes, and for P2 it might say no when given the program,

and the program has an input.

Now, what does that mean? So if halt says yes in the first line here, it would mean that program one stops

when given program one as an input. And of course, similarly, if halt says no, it would mean that P2 goes into an infinite loop

when given P2 or itself as an input.

Now we're going to do a very quick quiz here, because what I would like you to think about here for P1 and P2,

what inverse halt, when run on that program, actually does. So what does inverse halt do when it's run on P1?

And what does inverse halt do when it's run on P2?

So does inverse halt, when run on P1, halt or go into an infinite loop?

And does inverse halt, when run on P2, halt or go into an infinite loop?

So please check the one that is correct for each one.