In all of the input systems described here, romaji is converted into kanji, hiragana, or katakana . The relationship of the romanji to the Japanese character set can confusing. This can be especially difficult for members of the Linux-Nihongo community who may even great difficulty inputting their name and the names of their friends in katakana.
I'm including a section of Jeffrey Friedl's manual page for his excellent lookup program. Most of the romanji to Japanese conventions apply to the programs covered in this document.
Section From Jeffrey Friedl's Lookup manpage showing Japanese input