Representation On Computers
The letter Uk was first represented in Unicode 1.1.0 as U+0478 and 0479, (Ѹ ѹ). It was later recognized that the glyph to be used for the letter had not been adequately specified, and it had been represented as either a digraph or monograph letter in different released fonts. There was also the difficulty that in written texts the letter may appear in lowercase (ѹ), uppercase (Ѹ), or in all caps (ОУ), which was not allowed for.
To resolve this ambiguity, Unicode 5.1 has deprecated the use of the original code points, introduced the new U+A64A and A64B, (Ꙋ ꙋ), and recommends composing the digraph with two individual characters ⟨о⟩+⟨у⟩ .
However, the recommended method may cause some text representation problems. Actually there was not modern letter У in the Old Church Slavonic orthography, and its code point was replaced in different Old Slavonic computer fonts with digraph or monograph forms of the Uk or with the tailed form of Izhitsa. Tailed Izhitsa may be used as a part of the digraph, but using the shape of the monograph Uk as a part of the digraph Uk is incorrect.
The minuscule monograph Uk was used in the Romanian Transitional Alphabet to represent /u/, but due to font restrictions, the Ȣ ligature or Latin gamma are occasionally used instead.
Read more about this topic: Uk (Cyrillic)