In order to identify each specific computer connected to the Internet, a special addressing system was developed. There are two types of Internet addressing: numeric (IP addressing) and symbolic. These two systems exist in parallel. Numerical addressing is used by machines, symbolic - by people. Indeed, it is much easier for a person to remember and interpret symbols (letters) than numbers.
Any computer connected to the Internet has an IP address (short for Internet Protocol), which consists of four numbers separated by periods (XXXX.XXX.XXX.XXX). The information presented in this form fully identifies the address of the computer. Each number ranges from 000 to 255. Such Internet addressing is sufficient to encode four billion computers.
While the World Wide Web had a small number of subscribers, a digital system was quite enough, but with its expansion it became inconvenient to use such a model. And it was decided to use the Domain Name System DNS (from the English Domain Name System) in parallel . To do this, a group of people was assigned the responsibility of assigning unique names to users in a particular segment. There is no Internet control center in the world, but there are organizations that check and assign numbers: the domain name of the computer must be unique, and these organizations monitor it. Addressing on the Internet using domain names is the most widespread today.
A computer name can contain any number of domains, but most contain from two to five names that are separated by a dot (for example, tvka.ivno.ru. or www.companys.com). Such addresses have some analogy with the mail. In order to send a message to the right person, first indicate the country, then the region, district, settlement, street and the name itself. The Internet addressing has a similar hierarchy: on the right is the domain of the first (highest) level, followed by lower-level domains, which together create a unique computer name. The top -level domain name located on the right contains, as a rule, information about the geographic location of the computer (.ru - Russia, .by - Belarus, .ua - Ukraine, etc.) or about the topic the site is dedicated to (.gov - government structures; .com - commercial organizations; .org - non-profit organizations; .edu - educational institutions, etc.). But site owners do not always adhere to the accepted classification, and in the .RU zone a Belarusian, Kazakh or any other site may well be located.
Today there are so many addresses on the Internet that it is impossible to imagine a database that could contain all addresses, so a protocol has been developed by which a given name is searched. For this, a special program is installed on the provider's server, in which symbolic DNS addresses are converted to IP addresses. Then there is a search for the server on which information about the required site or mailbox is stored. This is actually a very difficult task: there are too many servers on the network. To simplify the search, use universal URL resource pointers (from Universal Resource Locator). Such an index contains information about the protocol that must be used when searching for the address, about the program needed for the search, and about the file where the necessary information is contained, which makes searching for a particular site much easier.