A terribly newbie question.

This is going to sound silly, but well, I've reached the end of my
patience hunting for the answer. Here goes:

I'm trying to learn C++. I'm running OS X. Can someone point me toward
a resource (or just tell me -- I'm quite willing to have the answer
just handed to me at this point) that will tell me, simply and
specifically, what compiler I should be using? None of my "Hello,
World!" exercises will compile.

Thanks.