[ptp-dev] Question about Fortran free vs fixed format parsing

[Dave Wootton <dwootton@xxxxxxxxxx>]

Hi
What controls whether the source in
a Fortran editor is parsed by fixed format or free format source file rules?
Is it by file extension or by some other means? If I create a .f source
file it seems to set up an editor with fixed format rules and a .f90 source
file seems to set up an editor with free format rules.

Is there a description somewhere that
explains the conditions under which the source format is selected?
Dave