How does GB 18030 relate to Unicode?
The specification refers directly to a mapping of GB 18030 codes to and from ISO 10646/Unicode to define most character assignments. Some characters that used to be mapped for GBK to the PUA (Private Use Area) for Unicode 2.1 are now assigned in Unicode 3.0, and their mappings from GB 18030 use only the Unicode 3.0 code points. In addition, GB 18030 defines roundtrip mappings for all 1.1 million Unicode code points including unassigned and non-character ones, but excluding single surrogates. This makes GB 18030 functionally very similar to a UTF.