HP Fortran Programmer's Guide (September 2007)

Compiling and linking
Compiling with the f90 command
Chapter 2 75
NOTE The compiler generates a .mod file for each file that defines a Fortran module.
It also reads the .mod files when compiling source files that use modules. Do not
specify .mod files on the command line. If you do, the compiler will pass them to
the linker, which will try (and fail) to link them into the executable. For more
information about .mod files, see “Compiling programs with modules” on
page 82.