How to tell if 64 bit vs 32 bit engine?

I did search the archives for this.... But didn't see a posting that directly answered the question.

How do I tell if the 32 bit version of PostgreSQL is running on a 64 bit machine, or if the 64 bit version was installed? Is there a pg_ table that I can query or a config file I can look in to find out? I found nothing in postgresql.conf that would indicate this.

Thanks,

Keaton