QString unicode

[ramin.lich]

i read in Qt docs about QString and found that QString supports unicode encoding but still when i write some stances in text file i see some "?" between words.
the language that i use is part of unicode here this is my code.

QFile dataF("fa.txt");
    dataF.open(QIODevice::WriteOnly | QIODevice::Append);
    QTextStream streamF(&dataF);
    streamF<<fa<<"\r\n";
    dataF.close();

QFile dataF("fa.txt");
    dataF.open(QIODevice::WriteOnly | QIODevice::Append);
    QTextStream streamF(&dataF);
    streamF<<fa<<"\r\n";
    dataF.close();

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im i miss something?
best regards