.dd part of the Federal Republic of Germany, which had already been assigned the ccTLD .de. The ISO 3166-1 code "DD" was withdrawn in 1990. .dd .dd was the assigned country code top-level domain (ccTLD) for the German Democratic Republic (East Germany). It was chosen based on the ISO 3166-1 alpha-2 code for the German Democratic Republic, the letters coming from the German name of the country: '. In accordance with IANA policy, .dd was therefore available to be assigned as the country code top-level domain (ccTLD) for East Germany. However, this was never done, and so .dd was never added
Country code second-level domain Country code second-level domain A country code second-level domain is a second-level domain to a country code top-level domain. Such a domain may be reserved by a domain name registry for the registration of third-level domains, or assigned to a third party as a subdomain. Many country code domain registries implement domain name classes at the second level underneath their ccTLD, such as are present in the original generic top-level domains com, net, and org, which were intended for commercial entities, network operators, and non-profit organizations, respectively. Many countries implement additional classes. For example, the United Kingdom (uk) uses co.uk