Lecture 4 Internet usage What is Internet

Lecture #4 Internet usage

What is Internet? Internet is a connection of computers and servers all over the world. So computers all over the world connects into huge network, which is called Internet

What is domain name? Domain name is the name of any web-site (which is stored on web-server) E. g. mail. ru domain name of server on which mail. ru is located Top-level-domains: org, com, asia, eu, kz, edu and etc. Second-level domains: mail. ru, vk. com Third-level domain names: docs. google. com

Domain name: some specific domain names Some country got domain names that can be suitable for some companies E. g. tv - domain name of Tuvalu receives 4 million $ each year for using its domain In some countries no one can buy domain name of second level, only 3 rd level domain names E. g. zaman. com. tr

If you have question? stackoverflow. com It features questions and answers on a wide range of topics in programming. Site serves as a platform for users to ask and answer questions Members can vote questions and answers up or down and edit questions and answers. Many other sub-sites which answers to different topics

Search engines http: //searchengineland. com/google-worlds-most-popular-search-engine-148089 Google: 1. 17 billion searchers, 76. 6% share Baidu: 293 million searchers, 19. 2% share Yahoo: 292 million searchers, 19. 2% share Microsoft: 269 million searchers, 17. 6% share Yandex: 74 million searchers, 4. 9% share Some specific notes: Baidu popular in China, Yandex is popular in Russian speaking countries

How does search engine searches? Crawling: crawler program finds all sites in the world and copies data to own servers Indexing: organizes data to serve responds quickly. E. g. save all sites with text “cats” into one server Serving results: When user enters search query, show out results in relevant order

What it needs to be good search engine? Relevance - shows “best” links first Natural language understanding - can understand language E. g. can understand “Windows 8” is about software, not about buying windows E. g. can understand that “змеиная голова” is same as “голова змеи”

Who are SEO specialists? People in this profession try to configure websites so that they are shown on first page for certain queries

Google phenomena: Why Google became successful Before Google there were bunch of search engines (Yahoo, Alta. Vista and etc. ) Mostly they showed irrelevant results. Google developed algorithm Page. Rank that could show relevant results and removed ads from search results It was developed by Larry Page and Sergey Brin while they were studying Ph. D at Stanford

Page. Rank algorithm

Email systems Before emails worked only if two users were online Today Email servers accept, forward, deliver, and store messages. Neither the users nor their computers are required to be online simultaneously; they need connect only briefly, typically to an email server, for as long as it takes to send or receive messages.

Social networks: personal Facebook - Most popular social network in the world VK. com - Most popular social network in russian speaking countries

Social networks: professional Linked. In is a social network for people in professional occupations. Connected by their professional links

Social networks: microblogging Twitter has limits on size of message 160 symbols Good for ?

Social network: photography Instagram - social network to share photographies edited with filters Was bought by Facebook for 1 billion $

>100 M active users http: //en. wikipedia. org/wiki/List_of_virtual_communities_with_more_than_100_million_active_users

Useful web applications Notes and reminder: Evernote Calendar: Google Calendar Document editing: Google Drive, Office 365 File storage: Dropbox, Google Drive

Online education edx. org - Harvard, Berkeley, Stanford and etc udacity. com - Developers from Google and etc. coursera. org - US universities and etc (about 500 courses)

Buy things in Internet? Things are bought by debit cards, which have cvv code (3 digits written on card) Pay. Pal is a service which stores your card’s info and when you buy something it takes money from your card and sends it to seller Why to use Pay. Pal? Pay. Pal can block account of seller and return your money in case of fraud