[R] Is there t.test with null hypothesis?

[Matti Viljamaa]

I’m trying to do a t-test, where the null hypothesis for the two data sets has to be:

“the means are the same”/“difference in means is equal to one”

Using the t.test function in R I’m able to see that it uses the following “alternative hypothesis”:

alternative hypothesis: true difference in means is not equal to 0

but does not seem to specify null hypothesis. I believe alternative and null hypotheses are different, although
I don’t exactly know how.

So what should I use for my t-test? Or is t.test ok?