NEC-LIST: Customized NEC files - opinions?

EZNEC pro programs can read and write files in standard NEC format. But
there are features in present and future versions of EZNEC that aren't
part of the standard NEC option set, such as MININEC type ground, and
more might be added in the future. I'd like to add information to the
NEC input file which can be read and used by the modified NEC code in
EZNEC to activate these features, but which would be ignored by standard
NEC programs. I'm sure that others have faced the same issue with
various customized versions of NEC.

I'd appreciate the group's thinking on the best way to do this, that is,
the way which is least likely to interfere with future NEC codes or
customized versions. Four ways come to mind:

1. Unused fields in existing cards, for example the third and fourth
integer fields in the GN card.
2. Special card types, such as "XY", that aren't currently used.
3. CM card with distinctive characters following CM, so that EZNEC would
recognize it as a special command card.
4. Special card types following the EN card.

The third option is almost certainly the safest with respect to
interfering with other special or future implementations, but might not
be the best for other reasons. What methods have others used?

If one doesn't already exist, it might be productive to establish at
least an informal standard for customization or NEC extenstions to
minimize the liklihood of interference between various customized
versions.

All comments are welcome.

Roy Lewallen

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