Since the 70s, different committees of the Department of Electronics and the Department of Official Language have been evolving different codes and keyboards which could cater to all the Indian scripts due to their common phonetic structure. Earlier efforts could not keep the ASCII code intact. The BIS standards IS 13194:1991 conforms to the earlier standard IS 10402:1982, ”8-bit coded character set for information interchange". It is intended for use in all computer & communication media which allow usage of 7 or 8 bit characters. In an 8-bit environment, the lower 128 characters are the same as defined IS 10315:1982, "7-bit coded character set for information interchange" also known as ASCII character set. The top 128 characters cater to all the ten Indian scripts based on the ancient Brahmi script. In a 7-bit environment the control code SI can be used for invocation of ISCII code set, the control code SO can be used for reselection of the ASCII code set.
The ISCII code table is a super-set of all the characters required in the ten Brahmi-based Indian scripts. An optimal keyboard overlay for these scripts is made possible by the phonetic nature of the alphabet. The differences between scripts primarily are in their written forms, where different combination rules get used.
There are manifold advantages in having a common code and keyboard for all the Indian scripts. Any software which allows ISCII codes to be used, can be used in any Indian script, enhancing its commercial viability. Furthermore, immediate transliteration between different Indian scripts becomes possible, just by changing the display modes.
The 8-bit ISCII code retains the standard ASCII code; while the Indian script keyboard overlay is designed for the Standard English can co-exist with Indian scripts. This approach also makes it feasible to use Indian scripts along with existing English computers and software, so long as 8-bit character codes are allowed.
The ISCII code (Indian Script Code for Information Interchange), co-exists with the standard English code: It contains only the basic alphabet arranged in an order which conforms to that in most of the Indian dictionaries.