Each subdirectory in this distribution represents the source files
as they should look prior to beginning the associated chapter.  You
can follow along with the book and fill out the source files to see
the library built piece-by-piece; alternately, you can download the
"after" distribution and see what each chapter's associated files
look like after the chapter is complete.

The files for the first five chapters are just Makefiles, header files,
and some blank source files with nothing but the header #include's 
filled in.  The later chapters start out with previous chapters
"after" material filled in.

Note that none of the subdirectories of this distribution will compile
as is; you'll need to follow the instructions in the associated chapters
before the directories will compile.  Alternatively, or if you get stuck,
take a look at the "after" distribution, whose contents are all
compile ready.