Hungarian has seven short vowels (a, e, i, o, u, ö, ü) including the front unrounded vowels ö and ü. The long equivalents of the first five are written with the acute accent (á, é, í, ó, ú). (The accented a and e is not really just a longer version but articulated differently.)
The double acute acts as combined acute with umlaut, giving the longer version of ö and ü.
The codes are supported in the ISO 8859-2 and UTF-8 codepages, the letters are: ő (U0151 LATIN SMALL LETTER O WITH DOUBLE ACUTE), ű (U0171 LATIN SMALL LETTER U WITH DOUBLE ACUTE), Ő (U0150, LATIN CAPITAL LETTER O WITH DOUBLE ACUTE) and Ű (U0170 LATIN CAPITAL LETTER U WITH DOUBLE ACUTE).
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