Country, Language and Currency Codes (ISO3166, ISO639 and ISO4217)

With this article I wanted to clarify how countries, languages and currency designations should actually be abbreviated correctly. This is especially important when working on international projects or with software components that adhere to these standards. For example, what do you think is the abbreviated 3-character code for the Latvian language: LAT or LAV? It turns out it's LAV, because LAT is the abbreviation for Latin :)