The FAR is chapter 1 of title 48 of the Code of Federal Regulations.
The DFARS is subchapter 2, etc..
Title 48 of the CFR is composed of the FAR and the agency FAR Supplements both. Why does one see the FAR composed of Subchapters A through H? Because the FAR itself is the Chapter level, i.e. Chapter 1.
The regulations that all executive agencies promulgate are published in the CFR (they are 'codified' there after first being published in the Federal Register). Some agencies get a whole CFR title to themselves, but in this case, the FAR is a regulation that is drafted by/applies to multiple agencies. GSA, Dod, and NASA share responsibility for maintaining it, so unlike some other CFR titles, this one is not specific to a single agency. See http://www.acquisition.gov/far/far_faqframe.html for frequently asked questions.