How to use have to, have got to and ought to.

Have to is used to talk about strong obligation that comes from somewhere else .For instance, this obligation from your guardian, Boss, workplace, school or from your parents.

Example:

Exp1: You have to have a bachelor degree in order to have a good job.

So here bachelor degree is the prerequisite of a good job.

Exp2: you have to go home by 9 pm. (your parents told it)

Similarly we can use have got to or ought to to make the same sense like have to.

More example:

I have got to get up early.

I ought to get up early.

I have to get up early.

the three sentences mentioned above have same meaning.

I don’t have to go there. (Negative)

Do I have to go there? (Interrogative)

Sorry I can't write anymore because my Skype friends are knocking, I have got to (Or have to or ought to) talk to them.