: C:\Program Files\Microchip\xc8\v2.40\include\xc.h
This package provides the development files for the X11 library, including header files like X11/Xlib.h , which might be what you're looking for or lead you to the correct path. xc.h library download
Would you like help finding an alternative to whatever functionality you thought xc.h provides? : C:\Program Files\Microchip\xc8\v2