RFC 4042:UTF-9 and UTF-18 Efficient Transformation...
RFC-Ref

SIP


Click on the red underlined text to get to the source

... codepoints in the Basic Multilingual Plane (BMP, plane 0), Supplementary Multilingual Plane (SMP, plane 1), Supplementary Ideographic Plane (SIP, plane 2), and Supplementary Special-purpose Plane (SSP, plane 14) in a single 18-bit ...



Google
Web
RFC-Ref