The Makefile supplied with the distribution of DDSCAT.5a is set up to link to a ``dummy'' subroutine dummywritenet.f instead of subroutine writenet.f, in order to minimize problems during initial compilation and linking. The ``dummy'' routine has no functionality, other than bailing out with a fatal error message if the user makes the mistake of trying to specify one of the netCDF options (ALLCDF or ORICDF). First-time users of DDSCAT.5a should not try to use the netCDF option - simply skip this section, and specify option NOTCDF in ddscat.par. After successfully using DDSCAT.5a you can return to §5.4 to try to enable the netCDF capability.