_ICONV_MODE environmental variable

The _ICONV_MODE environmental variable selects the behavior mode for the iconv_open(), iconv(), and iconv_close() family of functions. The _ICONV_MODE value can be set to:
C
Users have created their own iconv() converter(s). Search for user created converters first. If the user-created converter is not located, try using Unicode Conversion Services to perform the conversion.
Note: _ICONV_UCS2 and _ICONV_PREFIX environment variables will be honored while searching for user-created converters, but they will not be honored while using Unicode Convesion Services.
U
Use Unicode Conversion Services to perform all conversions not listed in the Table 2. This is the default value for _ICONV_MODE. The values of the _ICONV_UCS2 and _ICONV_PREFIX will not be honored.