It is possible to unambiguously encode an "unpaired surrogate" (a high surrogate code point not followed by a low one, or a low one not preceded by a high one) in the format of UTF-16 by using a code unit equal to the code point. The result is not valid UTF-16, but the majority of UTF-16 encoder and decoder implementations do this then when translating between encodings. Windows allows unpaired surrogates in filenames and other places, which generally means they have to be supported by software in spite of their exclusion from the Unicode standard.