0xD8000xDBFF

0xD8000xDBFF refers to the range 0xD800 through 0xDBFF, the high surrogate code units used in UTF-16 encoding. In Unicode, code points outside the Basic Multilingual Plane (U+10000 to U+10FFFF) are represented in UTF-16 as pairs of 16-bit units: a high surrogate in the range 0xD800–0xDBFF followed by a low surrogate in the range 0xDC00–0xDFFF.

A surrogate pair encodes a single Unicode scalar value. The code point U is computed from the pair (H, L) as U = ((H - 0xD800) << 10) + (L - 0xDC00) + 0x10000, where H is the high surrogate and L is the low surrogate. This mechanism allows representation of characters outside the BMP, such as many emoji and historic scripts.

High surrogates alone are not valid Unicode scalar values and should not appear as standalone characters. In well-formed text, a high surrogate must be followed by a corresponding low surrogate; unpaired surrogates are treated as errors or replaced with a placeholder during decoding. Consequently, surrogate code points are not used in UTF-8 or UTF-32 representations as standalone characters.

In practical computing, languages and environments that use UTF-16—such as Java, C#, and JavaScript—expose these code units. Strings may contain surrogate pairs; counting code points or iterating characters often requires special handling to combine the pair into a single character or to process code points directly.

Note that 0xD8000xDBFF is not a single code point but the high-surrogate range within UTF-16. The correct notation is the range 0xD800–0xDBFF.