itrans works by assigning every indian language letter an english equivalent. A transliteration table mapping devanagari characters into english equivalents is provided in the reference documents for the devanagari font: dvnc.itx for the Devnac font, and dvng.itx for the Devnag font. The tamil mapping is in the document tamil.itx.
itrans scans the input text for consonants, vowels, and special forms. Consonants suffixed with vowel codes create a complete composite character. Consonants may be suffixed with one or more consonants to create ligature forms. All this transliteration is automatically handled, and appropriate indian language characters are produced. If ligatures exist for a particular combination of consonants, they will be used automatically. If a ligature does not exist for some combination of the consonants, half-forms of the consonants will be used. The user can also override the ligature mechanism so that even if a ligature exists, the half forms of consonants will be used. Some languages such as tamil do not have any ligatures, in that case the appropriate action is taken — for tamil, a dot is printed on top of a consonant if it is not followed by a vowel form.
All these features make itrans an highly customizable and easy-to-use package. Even the transliteration map given here is not mandatory—the user can always edit the lexical source file and provide whatever mapping desired.
itrans is just a translation/char composition package. The task of actually placing characters on the page and spacing them correctly is left to other programs, such as TEX. TEX is the preferred interface, but, if absolutely necessary, and if the requirements of text placement are minimal, the dumb textual input interface could be used. This mode directly produces PostScript output, and contains minimal (read none) wordprocessing features; spaces and linebreaks in the input are copied to the output unchanged. This mode can only be used for fonts that are in PostScript itself, such as the devanagari font devnac that comes bundled with the system. Direct PostScript output cannot be produced for Metafont descriptions, such as the tamil wntml font.)
One important point to note is that since the current interface to this package is through an english language interface, it is quite clumsy and time consuming to start off writing a document or letter from scratch. I.e., thinking in marathi, and typing in english is quite slow! I find it much more easier and faster to write down a hand-written version of a document first, and then type it up in english, transliterating as I type. Of course, the problem could be attributed to my weak knowledge of marathi and hindi.