If you view writing in Bengali script on an iPhone you’ll pretty quickly notice a fundamental problem with the way it appears.
This has to do with vowels not being shown correctly and it occurs because of the type of fonts being used and the way they work.
There are two forms for writing Bengali vowels, a long and a short form. Vowels that appear after a consonant are shown in the shorter form, appearing as vowel marks or ‘kar’s. They are variously written before, after or under the consonant they actually follow when reading the word.
But on an iPhone the i-kar, e-kar and the vowel sign for the letter O, an e-kar before the letter followed by an a-kar after the letter, are all displayed incorrectly (see the above iTransliterate iPhone app screenshot).
There are some expansive and reasonably technical notes here on why Bengali and other Indian languages don’t appear properly on smart phones.
The link is to a blog post by Richard Ishida, who’s the internationalization activity lead at the W3C (World Wide Web Consortium) and also contributes to the Unicode Editorial Committee – which is a long-winded way of saying he knows what he’s talking about.
Ultimately though it’s a known issue with the fonts involved, and not a problem with your Bengali transliteration app, the mobile version of certain parts of this blog or BBC Bangla Tweets on an iPhone – all of which suffer from being incorrectly displayed at the moment.
The only good news about the problem is that if you are writing in Bengali script on an iPhone, with one of the transliteration apps say, if you email this writing to yourself, opening the email on a computer with Bengali fonts installed, the vowel signs will be correctly displayed.