A new flag, ‘-v’, has been added to ncgen to specify the file format variant. By default or if ‘-v 1’ or ‘-v classic’ is specified, the generated file will be in netCDF classic format. If ‘-v 2’ or ‘-v 64-bit-offset’ is specified, the generated file will use the new 64-bit offset format. To permit creating very large files quickly, another new ncgen flag, ‘-x’, has been added to specify use of nofill mode when generating the netCDF file.