FC -- Preferred executable for compiling ``Fortran`` language files. Will only be used by CMake on the first configuration to determine ``Fortran`` compiler, after which the value for ``Fortran`` is stored in the cache as :variable:`CMAKE_Fortran_COMPILER _COMPILER>`. For any configuration run (including the first), the environment variable will be ignored if the :variable:`CMAKE_Fortran_COMPILER _COMPILER>` variable is defined.