These files live in the msvcXX\mfc\include directory and include inline functions. These functions are only 'inline' during non-debug (_DEBUG is not defined) builds of MFC. They are prefaced with a special _AFX_INLINE directive which gets turned into 'inline' for non-debug builds and '' for debug builds.
MFC does this so you can debug into the functions in debug mode, but get the benefits of inlining during release builds. That's one of the reasons the library shrinks so much in release build mode.
scot@stingray.com, 7/20/95