The include file search path is the list of directories searched for INCLUDE files—file names appearing on preprocessor #include directives, or Fortran INCLUDE statements.
Example: Search for INCLUDE files in /usr/app/include:
demo% f95 -I/usr/app/include growth.F
Multiple -Ipath options may appear on the command line. Each adds to the top of the search path list (first path searched).
The search order for relative paths on INCLUDE or #include is:
The directory that contains the source file
The directories that are named in the -I options
The directories in the compiler’s internal default list
To invoke the preprocessor, you must be compiling source files with a .F, .F90, .F95, or .F03 suffix.