NetCDF evolves to keep up with needs of its users, and is actually:

• Two data models
  • Classic model (for netCDF-1, netCDF-2, netCDF-3)
  • Enhanced model (for netCDF-4)
• Four file formats
  • Classic format and 64-bit offset format variant
  • NetCDF-4 format and netCDF-4 classic model format variant
• Two independent flavors of application programming interfaces (APIs)
  • C-based (C, Fortran-90, Fortran-77, C++, Python, Perl, Ruby, Matlab, ...)
  • Java-based

You mostly don't need to be aware of these complications, because new versions of netCDF software support

• all previous netCDF data models
• all previous netCDF formats and their variants
• all previous APIs

Also, files written with any language API are readable through other language APIs.

2012 Unidata NetCDF Workshop > Overview of netCDF