/SOURCE_FORM

  Specifies whether all VSI Fortran source files on the F90
  command line are in fixed or free source form.

  FIXED
    Specifies that the input source files will be in fixed source
    form, regardless of the file type.  Source files with a file type
    of FOR or F (or any file type other than F90) are assumed to
    contain fixed source form.

  FREE
    Specifies that the input source files will be in free source
    form, regardless of the file type.  Source files with a file type
    of F90 are assumed to contain free source form.