About folders: cxx, fmk/include and blitz

[hugo_esquivel]

Hi Frank. This is a quick question. In the following lines, what do mean: cxx, include and blitz?
-I/usr/include/cxx
-I/Users/fmk/include
-I/Users/fmk/blitz

I mean, are these folders required for compilation process? If so, what do they contain?

Many Thanks!

PS: Lines extracted from Makefile.def (MACHINE_INCLUDES definition).

[fmk]

don't worry about them .. as i play with other packages, i sometimes leave the includes in the MAkefile.def