Well, no, actually - not in this case. The OP is transliterating from a "Romanized" (Latin-alphabet-based) "transcription" into Cyrillic. All characters in a given string will need to be replaced, because Cyrillic has its own dedicated "page" within the Unicode table. The incoming Latin characters (and diacritic marks) may come from the ASCII table or somewhere else, but when the transliteration is finished, every character will have been replaced.