Preprocess and compile Fortran source files, then assemble and link them together. More information: https://gcc.gnu.org/wiki/GFortran.
gfortran path/to/source1.f90 path/to/source2.f90 ... -o path/to/output_executable
gfortran path/to/source.f90 -Wall -g -Og -o path/to/output_executable
gfortran path/to/source.f90 -o path/to/output_executable -Ipath/to/mod_and_include -Lpath/to/library -llibrary_name
gfortran -S path/to/source.f90
gfortran -c path/to/source.f90