Since the late 18th century, Sanskrit has been transliterated using the Latin alphabet. The system most commonly used today is the IAST (International Alphabet of Sanskrit Transliteration), which has been the academic standard since 1888. ASCII-based transliteration schemes have also evolved because of difficulties representing Sanskrit characters in computer systems. These include Harvard-Kyoto and ITRANS, a transliteration scheme that is used widely on the Internet, especially in Usenet and in email, for considerations of speed of entry as well as rendering issues. With the wide availability of Unicode-aware web browsers, IAST has become common online. It is also possible to type using an alphanumeric keyboard and transliterate to Devanagari using software like Mac OS X's international support.

Answer this question, if possible (if impossible, reply "unanswerable"): What system of transliteration is not commonly used on the internet or e-mail?
unanswerable