Bamini is a Tamil ASCII font family. Tamil is typed on a normal keyboard in Bamini, the file stores English letters, and the font draws Tamil. Its layout follows the Tamil typewriter keyboard, which made it a natural fit for typists trained on typewriters.
Tamil carried several competing legacy encodings before Unicode became dominant: TSCII, TAB/TAM, Bamini, Vanavil, Kalaham and others. A document is only readable in the font it was typed in, so choosing the right converter matters. Bamini is not interchangeable with TSCII or TAB.
Tamil’s pre-base vowel signs (ெ, ே, ை) and split vowels (ொ, ோ, ௌ) are typed before the consonant in Bamini, and Unicode needs them after it. This reordering is the main reason a simple find-and-replace produces broken Tamil.