Some old text documents working with Arabic or Indic languages use 8-bit encoding, which required to use proprietary fonts. Such fonts can only use 256 glyphs, which is not sufficient for correct rendering of Devanagari (or other 10 Indic writing scripts). The various non-standard 8-bit encodings has been rendered obsolete by Unicode, which assigns each character a unique numeric value and name. Unicode standard provides the capacity to encode all of the characters used for the written languages of the world. TPTQ Arabic doesn't support the legacy 8-bit formats, instead to recommends to use Unicode standards, and Unicode compliant fonts.
The Indian government (Ministry of Communications & Information Technology) issued recommendation to use Unicode to represent Indic scripts.