Geographical data encoding (standard codes for countries/regions/cities)

Question

is there a standard way to encode the user location (country, state/region, town), so that I can ask the user to select these items upon registration and then use this data to show his location on the map?

Answer 1

The ISO 3166 specification is the widely accepted standard for country and "primary subdivision" (i.e. state, province, canton, etc.) codes. Note that this is different than storing address data.