Internet information resources. Information resources and services Information resources and Internet services

World Wide Web The World Wide Web (WWW) is a service for network users to gain access to information resources stored on computers in different parts of the world. The basis of the WWW are Web pages and Web sites. The presentation of information on the WWW is based on the capabilities of hypertext links. Hypertext is text that contains links to other documents. This allows you to easily and quickly move from one document to another. Linked documents can be scattered across the globe.

The address of a document on the Internet - its URL (Uniform Resource Locator - universal resource locator) consists of the following parts: The domain name of the server with a sign / at the end of the name The full name of the file on the server where it is located The name of the protocol with the signs // at the end of the name Consider example address (URL): fcior.edu.ru/card/701/algebraicheskie-uravneniya.html The entry indicates that this is a Web page (HTTP protocol - Hyper Text Transfer Protocol - hypertext file transfer protocol). The domain name of the server on which the page is stored. The full file name, including the path to the file, that is, all the directories that should be sequentially entered to open the required file. Internet address of the document

A.net Bftp C:// Ghttp D/ E.org Жtxt Solution. The first part of the file address is the name of the protocol: GV txt.org SAME /ftp DB.net A The second part of the address is the name of the server (the computer on which the file is located): The third part of the address is full name file on the computer: Solving the problem Task 2. Access to the ftp.net file located on the txt.org server is carried out via the http protocol. In the table, fragments of the file address are encoded with letters from A to J. Write down the address specified file on the Internet and a sequence of letters encoding this address. Answer: GVZHEDBA.

Electronic mail Electronic mail () is a system for exchanging messages (letters) between subscribers of computer networks. High speed forwarding messages Possibility of sending attached files containing graphics, sound Possibility of simultaneous sending of letters to several recipients at once Advantages Email Any Internet user can create their own Mailbox- a named area of disk memory on the mail server of your provider, where incoming and outgoing correspondence will be placed.

@. Username Domain name Country code Email address The email address looks like: The first part is selected by the user; the second part is tightly connected to the server on which the user registered his mailbox. The separator between parts of the address is

The sender types a message, specifies the recipient's address and sends the letter to the outgoing mail server. The outgoing mail server sends the message to the specified address. Over the Internet, the letter is transmitted to the incoming mail server specified in the recipient's address. The incoming mail server places the letter in the recipient's mailbox. The recipient opens his mailbox and gains access to the messages received by him. letters Scheme of e-mail operation

Nowadays, the service of instant exchange of small text messages in real time has become widespread. ICQ is the most famous program used for this purpose. Each ICQ user is assigned a personal ICQ number. Unlike e-mail, which has the ability to delay message delivery, messages in ICQ are transmitted in real time. Instant messaging

Network collective interaction Forms of collective interaction Teleconference Forum Chat Social network A system for exchanging information between network users. Unlimited in time Offers a set of sections for discussion. Real-time group communication service Interactive multi-user Web sites

Questions and tasks Describe the organization and purpose of the service. Is it a browser? Give examples of browsers. What documents are called hypertext? The table shows queries to the search server: 1 bulldog & collie & grooming 2 bulldog & collie 3 collie 4 collie | care Graphically depict the number of pages that will be found search server for every request. Arrange the query numbers in descending order of the number of pages that the search engine will find for each query. What is a URL? What is its structure? Analyze the addresses of the following documents: 1) september.ru/2007/11/01. htm 2) html 3) html On the edu.ru server there is a file demo.rar, accessed via the ftp protocol. Address fragments this file are encoded with letters from A to J. Write down the sequence of these letters that encodes the address of the specified file on the Internet. A.rar Bdemo C:// D/ Dftp E.edu Zh.ru What protocols are used to allow users to access information stored in file archives? What are the main advantages of email over regular mail? What is the structure of an email address? Describe in general terms how email works. Imagine that you need to contact a stranger or a very busy person. Did you manage to get the number? mobile phone and that person's email address. What type of communication do you think is more convenient to use in this situation? Justify your answer. What methods are there for working with email messages? Analyze the advantages and disadvantages of each of them. What are the similarities and differences between such forms of online collective interaction as teleconference, forum and chat? What do you know about social networks? What is a login? Is it possible to use the same login on different sites? What is a password? What rules should you follow when choosing a password? Why is it not recommended to use the same password on different sites? What is the basic rule of netiquette? What is spam? Find out the history of this term.

World Wide Web The World Wide Web (WWW) is a service for network users to gain access to information resources stored on computers in different parts of the world. The basis of the WWW are Web pages and Web sites. Task 1. The table shows queries to the search server. To indicate logical operation OR queries use the | symbol, and the logical AND operation uses the & symbol. 1France | Spain | History 2France & Map & History 3France | History 4France & History Graphically display the number of pages that a search engine will find for each query. Arrange request numbers in descending order of number of pages.

Answer:)2)3)4) France Spain History France History France History Map Solving problem 1France | Spain | History 2France & Map & History 3France | History 4France & History

A.net Bftp C:// Ghttp D/ E.org Жtxt Solution. The first part of the file address is the name of the protocol: GV txt.org SAME /ftp DB.net A The second part of the address is the name of the server (the computer on which the file is located): The third part of the address is the full name of the file on the computer: Solving the problem Task 2. Access to the ftp.net file located on the txt.org server is carried out via the http protocol. In the table, fragments of the file address are encoded with letters from A to J. Write down the address of the specified file on the Internet and the sequence of letters encoding this address. Answer: GVZHEDBA.

File archives FTP authorization General scheme FTP operation Data transfer to active mode Transferring data to a server Transferring data between two FTP servers File archives are a kind of library storing files with software, graphics, music and other information. Access to files in file archives is possible using the following protocols: HTTP – hyper transfer protocol text documents; FTP is a special file transfer protocol.

File archives ftp:// com.edu/ htm.exe ProtocolServerFile The address of a file on a file archive server includes the file access protocol, the server name, and the full file name. Many files received via FTP are compressed. Their names end with the extensions zip, arj, rar, etc. After copying compressed file it should be unpacked, that is, restored to its original form.

Electronic mail Electronic mail () is a system for exchanging messages (letters) between subscribers of computer networks. High speed of message forwarding Possibility of sending attached files containing graphics, sound Possibility of simultaneous sending of letters to several recipients at once Advantages of e-mail Any Internet user can create his own mailbox - a named area of disk memory on the mail server of his provider, where incoming and outgoing correspondence will be placed.

Mail protocols Electronic mail uses two protocols: SMTP protocol - for sending mail; POPZ protocol - for receiving mail. Since anyone has the right to send mail to anyone, the SMTP protocol does not require identification of the sender. The letter should be received by the person to whom it is addressed; This requires identification of the recipient (by login and password), which is provided by the POP3 protocol. Mail server User 1 User 2 SMTP SMTP POP

Viewing messages MethodAdvantagesDisadvantages Mail client Internet connection while messages are downloaded Access to mailbox only from a computer with an installed mail client Web interface Access to mailbox from any computer To read correspondence you need a network connection Methods of viewing messages

Nowadays, the service of instant exchange of small text messages in real time has become widespread. ICQ is the most famous program used for this purpose. Each user is assigned an ICQ personal number ICQ. Unlike e-mail, which has the ability to delay message delivery, messages in ICQ are transmitted in real time. Instant messaging

Netiquette There are unspoken rules of conduct on the Internet, the so-called netiquette. Briefly, the essence of netiquette can be expressed in one phrase: “Respect your invisible partners on the Internet!” Basic rules of netiquette Clearly identify yourself Know and respect your recipient Indicate the subject of the message Write correctly You can express emotions using emoticons Do not ask for confirmation of receipt of a message unnecessarily Avoid spam Do not expect complete confidentiality of correspondence

The most important thing is that a document posted on the Internet has a URL. Users can access documents posted on Web sites using the HTTP protocol. File archive is a storage on the Internet of files with software, graphics, music and other information. Access to file archives is possible via the FTP file transfer protocol. Electronic mail () is a system for exchanging messages (letters) between subscribers of computer networks. The main forms of collective interaction are teleconferences, forums, chats, social media.

Questions and tasks Describe the organization and purpose of the service. Is it a browser? Give examples of browsers. What documents are called hypertext? The table shows queries to the search server: 1 bulldog & collie & grooming 2 bulldog & collie 3 collie 4 collie | care Graphically depict the number of pages that the search engine will find for each request. Arrange the query numbers in descending order of the number of pages that the search engine will find for each query. What is a URL? What is its structure? Analyze the addresses of the following documents: 1) september.ru/2007/11/01.htm 2) 3) On the edu.ru server there is a file demo.rar, accessed via the ftp protocol. Fragments of the address of this file are encoded with letters from A to J. Write down the sequence of these letters that encodes the address of the specified file on the Internet. A.rar Bdemo C:// D/ Dftp E.edu Zh.ru What protocols are used to allow users to access information stored in file archives? What are the main advantages of email over regular mail? What is the structure of an email address? Describe in general terms how email works. Imagine that you need to contact a stranger or a very busy person. You were able to obtain the person's mobile phone number and email address. What type of communication do you think is more convenient to use in this situation? Justify your answer. What methods are there for working with email messages? Analyze the advantages and disadvantages of each of them. What are the similarities and differences between such forms of online collective interaction as teleconference, forum and chat? What do you know about social networks? What is a login? Is it possible to use the same login on different sites? What is a password? What rules should you follow when choosing a password? Why is it not recommended to use the same password on different sites? What is the basic rule of netiquette? What is spam? Find out the history of this term.

The World Wide Web (WWW) is a service for network users to gain access to information resources stored on computers in different parts of the world. The basis of the WWW are Web pages and Web sites. Background Note The FTP file transfer protocol provides access to file archives of software, graphics, music, and other information. The exchange of messages (letters) between subscribers of computer networks is carried out via electronic mail (e-mail). Teleconferences, forums, chats, social networks are the main forms of collective interaction on the Internet.

Sources of information 1. 7a75fef34e81/ftp3.swf - FTP authorization – connections 7a75fef34e81/ftp3.swf 2. c3cdcc5ba1a1/ftp1.swf - General scheme of FTP operation http://files.school-collection.edu.ru/dlrstore/fb31e305-aee0- 430e c3cdcc5ba1a1/ftp1.swf 3. d8ba87868f1d/ftp4.swf - data transmission in active mode d8ba87868f1d/ftp4.swf bff6f/ftp5.swf - data transmission in passive mode bff6f/ftp5.swf c8f9dc74/ftp8.swf - transmission and data to the server 5649c8f9dc74/ftp8.swf c362d3a/ftp2.swf data transfer session between two FTP servers c362d3a/ftp2.swf 7. a348f7100c4e/ftp4.swf - data transmission in active mode a348f7100c4e/ftp4.swf ba2361f41/ftp5.swf - data transmission in passive mode 538ba2361f41/ftp5.swf network etiquette eaf.jpg - logo email 7eaf. jpg 11. if - Microsoft-Outlook-Express logo http:// if

Sources of information Mozilla Trunderbird logohttp://warezatut.net/uploads/posts/ / jpeg 13. ze=article_large mail.ru logohttp:// ze=article_large 14. avait.jpg - ICQ logohttp://images.lpcdn.ca/ 924x615/201106/02/ avant-reseaux-sociaux-y- avait.jpg envelope server computer network server

Internet information resources

The World Wide Web

The global Internet attracts users with its information resources and services, which are regularly used by about a billion people in all countries of the world.

The rapid development of the Internet, which has been taking place over the past 15 years, is primarily due to the emergence of the World Wide Web. "World Wide Web" is a loose translation of the English phrase "World Wide Web", which is often referred to as WWW or Web.

World Wide Web technology. The World Wide Web uses hypertext technology in which documents are linked together using hyperlinks.

As link pointers Web pages may use text fragments that are highlighted with color and underlining, as well as graphic images, which are highlighted by a frame. Activating the link pointer on the source Web page (for example, by clicking the mouse) causes a transition to the desired Web page (Fig. 6.10).

The World Wide Web- these are hundreds of millions of Internet Web servers containing hundreds of billions of Web pages that use hypertext technology.

The web page can be multimedia, i.e. it can contain various multimedia objects: graphic images, animation, sound and video.

The web page can be interactive, i.e., contain forms with fields that are used when registering users of free email, when making purchases in online stores, etc.

Topically related Web pages are usually presented in the form Website, i.e., an integral system of documents interconnected into a single whole using links.

Web page address. Currently, a huge number of Web pages are stored on Internet Web servers. You can find a Web page on the Internet using the Web page address.

Web page address includes how the document is accessed and the name of the Internet server on which the document is located.

HTTP (Hyper Text Transfer Protocol) is used as a method to access Web pages. When recording a protocol, his name is followed by a colon and two forward slashes: http://

As an example, let's write down the address of the title page of the Web site "Computer Science and Information Technologies." The page is located on the server iit.metodist.ru, therefore, the address takes the form:

http://iit.methodist.ru

Browsers. Browsing Web pages is done using special programs viewing - browsers. Currently the most common browsers are Internet Explorer, Mozilla and Opera.

The browser window (Fig. 6.11) contains standard elements application windows:
- window menu containing sets of commands File, Edit, View, Favorites, Service And Reference;
- a toolbar whose buttons allow you to move from one Web page to another (buttons Forward, Back, Home), as well as manage the process of downloading them (buttons Stop, Refresh);
- text field Address:, in which the Internet address of the desired Web page is entered from the keyboard or selected from the list;
- the work area in which Web pages are viewed.

Rice. 6.11. Internet browsers Explorer, Mozilla and Opera

Virtual travel around World Wide Web. If your computer is connected to the Internet, you can launch one of the browsers and go on a virtual journey through the World Wide Web. The initial Web page will be automatically loaded into the browser (the address of the Web page from which the journey begins can be changed using the browser settings).

When a Web page is opened in a browser on a user's computer, it travels a long way from a remote Internet server through information transmission channels through several intermediate Internet servers. The loading speed of a Web page does not depend on the distance to the Web server, but on the number of intermediate servers and the quality of the communication lines through which information is transmitted from server to server. There may be a situation where a Web page loads much faster from a server located on another continent than from a server located down the street.

To go to another Web page in the text field Address: you must enter its Internet address. Many Web pages contain hyperlinks to other Web pages, so you can continue your journey on the World Wide Web by activating one of them.

In the process of reading a book (textbook, reference book, encyclopedia), quite often you need to return to the material you read. To quickly find the desired page, so-called “bookmarks” are often inserted into the book. While traveling on the World Wide Web, it is advisable to save Internet addresses of interesting Web pages as “bookmarks” in your browser. To visit such a page, it will be enough to activate one of the “bookmarks”.

Control questions

1. What function do hyperlinks perform in World Wide Web technology?

2. What parts does a Web page address consist of?

6.5. Short answer task. Write down the address of a Web page stored on an Internet server registered in the first-level domain ru, the second-level domain schools and having its own name www.

Email

Electronic mail (e-mail) is the most common Internet service. She is historically the first information service computer networks and does not require high-speed and high-quality communication lines.

Email has several major advantages over regular mail. The most important of them is the speed of message forwarding. If a letter by regular mail can take days and weeks to reach the addressee, then a letter sent by e-mail reduces the transmission time to several tens of seconds or, in the worst case, to several hours.

Another advantage is that email may contain not only a text message, but also attached files (programs, graphics, sound, etc.). In addition, e-mail allows you to send a message to several subscribers at once, forward letters to other addresses, etc.

E-mail address. In order for an email to reach its recipient, it must, in addition to the message itself, contain the email address of the recipient of the letter.

The first part of the usename email address is arbitrary and is set by the user himself when registering a mailbox. The second part server.ru is the name mail server Internet on which the user registered his mailbox.

E-mail address is written in a specific form and consists of two parts separated by the @ symbol: [email protected]

The email address is only recorded with Latin letters and must not contain spaces. For example, if the mail server is named metodist.ru, then the names of user mailboxes will look like:

[email protected]

Email addresses of subscribers are stored on the user's computer in a database " The address book". The subscriber's name, email address, phone number and other data are entered into the address book (Fig. 6.12).

Rice. 6.12. Address Book Database

Functioning of email. An Internet user can register a mailbox on the provider's mail server, which will store sent and received emails.

Created using an email program postal message on your local computer. At this stage, in addition to writing the text of the message, you must indicate the address of the message recipient (can be taken from the "Address Book"), the subject of the message and, if necessary, attach files to the message.

The process of sending a message begins by connecting to the Internet and delivering the message to your mailbox on a remote mail server. The mail server will immediately send this message through the Internet mail server system to the recipient's mail server in his mailbox.

To receive a letter, the recipient must connect to the Internet and deliver mail from his mailbox on a remote mail server to his local computer (Fig. 6.13).

Mail programs usually also provide the user with numerous additional services for working with mail (selecting addresses from the address book, automatic mailing messages to the specified addresses, etc.).

Outlook Express mail program. To work with e-mail, special mail programs are required. The Outlook Express email program, which is part of operating system Windows. After launching Outlook Express, an application window appears, which consists of four parts (Fig. 6.14).

Rice. 6.14. Outlook Express window

In the upper left part of the window there is a list of folders in which emails are stored:
- Inbox- contains received letters;
- Outgoing- contains sent letters, from the moment of creation until the moment of delivery from local computer user to the provider's mail server;
- Sent- contains all letters delivered to the mail server;
- Deleted- contains deleted emails;
- Drafts- contains letter templates.

The user can create their own folders to store thematically grouped emails.

The lower left side of the window contains a list of contacts, which provides access to information stored in the Address Book database (email addresses, phone numbers, etc.).

The right window is divided into two parts. A list of messages stored in the selected folder is displayed at the top.

The contents of the highlighted message are displayed at the bottom of the right window.

Email with a Web interface. Some mail servers provide users with the ability to work with e-mail using a Web interface. Work with Web mail can be done using any browser. An essential feature of Web mail is that all messages are permanently stored on a remote mail server, and not on the user's local computer.

Many Web mail servers offer everyone the opportunity to register a free mailbox. Registered users must enter their login And password, after which they can log into the mail system. A registration procedure is offered for new users (Fig. 6.15).

Rice. 6.15. Login to Webmail

Control questions

1. What advantages does email have over regular mail?

2. What parts does an email address consist of?

3. How does email work?

Tasks for independent completion

6.6. Short answer task. Record the email address registered by user fio on the zmail.ru mail server.

File archives

File archive servers. Tens of thousands of Internet servers are file archive servers, storing hundreds of millions of files various types(programs, device drivers, graphics and sound files etc.). The presence of such file archive servers is very convenient for users, since many necessary files can be “downloaded” directly from the Internet.

File servers are supported by many software companies and computer hardware manufacturers. peripheral devices. The software hosted on such servers is freely distributed or shareware and therefore, by “downloading” this or that file, the user does not violate the law on copyright for software.

File download managers. For the convenience of users, many file archive servers (freeware.ru, www.freesoft.ru, www.download.ru) have a Web interface, which allows you to work with them using browsers. Browsers are integrated systems for working with various Internet information resources and therefore include file download managers.

However, it is more convenient to work with file archives to use specialized file download managers that allow you to continue downloading a file after the connection to the server is broken. File download managers provide the user with detailed information in numerical and graphical form about the file download process (file volume, volume of the downloaded part, including as a percentage, download speed, elapsed and remaining download time, etc.).

Some file download managers achieve increased download speed by splitting the file into parts and downloading all parts at the same time. For example, in the FlashGet file download manager, the process of downloading each part of a file is presented in graphical form at the bottom of the application window (Figure 6.16).

Address of the file on the file archive server. Access to files on file archive servers is possible both via HTTP and the special FTP file transfer protocol (File Transfer Protocol). The FTP protocol allows you not only to download files from remote servers file archives to the local computer, but also vice versa, transfer files from the local computer to a remote server.

File address includes how the file is accessed and the name of the Internet server on which the file is located.

If the FTP file transfer protocol is used as a method of accessing the file file.exe stored on the ftp.metodist.ru server, the file address will be written as follows:

ftp://ftp.metodist.ru/file.exe

Control questions

1. What files are typically stored on file archive servers?

2. What parts does the address of a file on a file archive server consist of?

Tasks for independent completion

6.7. Short answer task. Write down the address of the program.exe file stored on a computer registered in the first-level domain w, second-level domain schools and having its own name ftp.

Chatting in Internet

Recently, real-time communication on the Internet has become increasingly widespread. Increased data transfer speeds and increased computer performance give users the opportunity not only to exchange text messages in real time, but also to carry out audio and video communications.

Real-time communication servers. There are thousands of servers on the Internet that provide real-time communication. Any user can connect to such a server and start communicating with one of the visitors of this server or participate in a group meeting.

The simplest way to communicate "talk", or chat(English chat) is the exchange of messages typed from the keyboard. You enter a message using the keyboard, and it appears in a window that all meeting participants can see at the same time.

If your computer, as well as the computers of your interlocutors, are equipped sound card, microphone and headphones or acoustic speakers, then you can exchange audio messages. However, a “live” conversation is possible only between two interlocutors at the same time.

In order for you to be able to see each other, i.e. exchange video images, Web cameras must be connected to your computers.

Interactive communication using the ICQ system. In recent years, interactive communication through ICQ servers(this three-letter abbreviation is formed from the consonance of the words “I seek you” - “I am looking for you”).

The ICQ interactive communication system integrates various forms of communication: email, text messaging (chat), Internet telephony, file transfer, searching for people on the network, etc. (Fig. 6.17).

Rice. 6.17. ICQ interactive communication program

Currently, there are almost 200 million registered users in the ICQ system, and each user has a unique identification number. After connecting to the Internet, the user can start communicating with anyone registered in the ICQ system and connected to this moment to the Internet by the user.

Internet telephony. Internet telephony is used to transmit voice data over the Internet computer network. Internet telephony providers use special equipment to connect the Internet computer network and the regular one. telephone network. The user can use Internet telephony services and call directly from a computer (see Fig. 6.18) or from a regular telephone, having previously dialed the number of the Internet telephony provider.

It is beneficial to use Internet telephony for calls to remote settlements and countries of the world, since a minute of such communication is significantly cheaper than long-distance and international tariffs telephone communication.

Control questions

1. What forms of real-time communication exist on the Internet?

Mobile Internet

Mobile telephone network. Currently, the mobile telephone network has covered almost the entire world, and the number of mobile phone users is approaching one billion people. Information exchange between mobile phones is carried out using a network consisting of station antennas cellular communication, interconnected by information transmission channels.

Net mobile communications allows you to transmit not only voice messages, but also data. You can exchange short text messages using mobile phones SMS, and multimedia messages MMS, which allow you to send phone ringtones and graphics (such as photos taken with your phone's built-in camera).

Data exchange between the mobile telephone network and the Internet computer network. The mobile telephone network and the Internet computer network allow the transmission of data and voice messages, and therefore it is advisable to combine their information resources. Mobile telephone operators and Internet providers provide the ability to transfer data between these networks (Figure 6.18).

Data exchange between networks allows, for example, from a mobile phone to send email messages to a mailbox on the Internet, and from a computer connected to the Internet to send SMS messages to a mobile phone.

Internet access using a mobile phone. Many mobile phone models have a built-in modem, so for wireless access To access the Internet, just connect your mobile phone to your computer and call your provider. After connecting your computer to the Internet, you can “travel” the World Wide Web, work with e-mail, “download” files and use any other Internet resources, as with a regular cable connection. The disadvantage of this connection is the low data transfer speed (no more than 9.6 Kbps) and the high cost per minute of connection.

Full high-speed Internet access from a mobile phone can be achieved using technology GPRS, at which the maximum possible data transfer rate is 170 Kbps (this is approximately 3 times faster than dial-up access). Importantly, this technology provides immediate access to the Internet, without the need to dial an Internet provider, and allows you to simultaneously talk on your mobile phone and exchange data between your computer and the Internet.

Connecting a mobile phone to a computer can be done in various ways: using a cable to the COM port, using a cable to the USB port, or wirelessly to the infrared port (Fig. 6.19).

To access Internet information resources directly from mobile phones, you can use WAP-browsers. WAP sites are specially adapted to the capabilities of a mobile phone (two-color graphics, small screen and small memory) and contain news, weather forecasts, exchange rates, etc. From WAP sites you can send an email message or participate in a WAP chat.

Control questions

1. What is the difference between Internet telephony and mobile Internet?

2. What data can be transferred from a mobile telephone network to the Internet computer network? From the Internet to the mobile network?

Sound and video on the Internet

Sound and video files have a large information volume. Transferring such files over computer networks in standard digital formats requires high-speed communications links. throughput. Digital stereo sound High Quality with a sampling rate of 48000 times per second and an encoding depth of 16 bits requires a data transfer rate equal to:

16 bits × 48,000 s -1 = 1,536,000 bps = 1500 Kbps » 1.5 Mbps.

Digital video of the television standard requires a data transfer rate of about 240 Mbit/s to transmit images.

To reduce the volume of audio and video files without visible loss of quality, special file compression methods are used, based on the removal of audio or video information that is not perceptible to humans.

Stream audio and video. Transfer technologies have become widespread on the Internet streaming audio and video. These technologies transfer audio and video files in parts to the local computer buffer, which makes them possible to stream even when using a modem connection. Reducing the transmission speed of the channel can lead to temporary audio dropouts or skipped video frames.

To listen to streaming audio and watch streaming video, use multimedia players ( Windows Media Player, WinAmp, etc.). While playing a streaming media file, the user receives information about the data transfer rate and can adjust the playback quality.

There are quite a lot of radio and television stations that broadcast via the Internet. Web cameras are widely popular, installed in various parts of the world (on city streets, in museums, in nature reserves, etc.) and continuously transmitting images (Fig. 6.20).

Control questions

1.Why is it necessary to compress audio and video files when transmitting over the Internet?

Committee of General and Professional Education of the Leningrad Region

Leningrad Regional Institute for Educational Development

Yurkov A.V.

INFORMATION RESOURCES AND SERVICES

INTERNET NETWORKS

Tutorial

Saint Petersburg

Published by decision of the Faculty of Informatization of Education
and RIS LOIRO

Reviewers: O.N.Shilova, Doctor of Pedagogical Sciences, Professor of the Russian State pedagogical university them. A.I. Herzen, M.A. Goryunova, Dean of the Faculty of Informatization of Education

Yurkov A.V. Using information resources on the Internet. Tutorial. SPb.: LOIRO, 2003.

The textbook aims to introduce students to the structure of Internet information resources, work in standard browsers, techniques for searching for information using popular information search engines, working with e-mail and other online services that provide information exchange and communication capabilities, as well as legal issues of the Internet.

Recommended by the educational and methodological office of information and communication technologies as teaching aid for students of advanced training courses at LOIRO and regional centers information technologies.

 Leningrad regional
Institute for Educational Development
(LOIRO), 2003

 A.V. Yurkov

What is the Internet? 4

Internet navigation 4

WWW 7 address structure

Problem with Cyrillic 8 encodings

Searching for information on the Internet 8

Search engines 8

Popular IPS 9

Simple search 10

Advanced search 12

Internet information resources 14

Some useful addresses 14

“Pumping” information 15

Internet and law 15

Tasks for practical work: 16

Internet services and working with them 18

Email 18

Creating an email address 18

Create and send emails 18

Antivirus prevention 20

Reception of electronic messages. Work with mail programs 21

Encoding problem 25

Teleconferences. Forums. Chats. 26

Netiquette 29

Email Etiquette Rules Email 29

Teleconferencing Etiquette Rules 30

Chatting etiquette rules 31

Working with FTP archives 31

Tasks for practical work: 34

Literature and Internet resources 35

Internet Basics

What is the Internet?

The Internet is a global network of computer networks connected by communication channels and transmitting information to each other according to certain rules, called protocols. Ordinary telephone lines can also be used as communication channels. To connect your computer to the network via telephone line a device called a modem is used (from the words modulation/demodulation - conversion digital information, processed by computer, into analog telephone signals). Organizations called providers provide access to the Internet.

The birth of the Internet dates back to 1969, when the first network was created to connect geographically remote computers. Currently, the most rapidly developing information resource and Internet service is W orld W ide W eb (WWW) or “World Wide Web”, which emerged in 1993 1

The WWW system is based on four basic concepts:

hypertext;
unified document format (HTML);
one system addressing (URL).
programs for viewing documents (browsers);

The World Wide Web today is not only a huge amount of diverse information, but also new multimedia 2 technologies for its transmission, which make it possible to talk about the Internet as a “virtual” reality - a new way of communication and coexistence of people.

Keywords:

The World Wide Web
uniform resource locator (URL)
HTTP protocol
file archives
FTP protocol
Email
forum
teleconference
social network
login
password

The Internet attracts users with its information resources and services, the most popular of which are currently:

The World Wide Web;
file archives;
Email;
collective interaction services (forum, teleconference, chat, social network).

In order to use Internet services, you must go through authorization on the relevant sites, that is, enter your username and password in a special form.

Login- this is a combination of various symbols that the service associates with the user; in other words, this is the username under which other network users will “see” him. Therefore, the login should not be an incoherent set of characters; It is desirable that the login be memorable and somehow associated with the user. The login must be unique. The same login can be used on different sites and services.

Password- this is a combination of various symbols confirming that it is the owner of the login who intends to use the login. The password should be known only to the user and be such that it is difficult for others to guess. It is advisable to adhere to the following rules when creating a password:

the password must not be the same as the login;
the password must consist of at least six characters (letters, numbers, punctuation marks, etc.);
the characters in the password must not form any words, numbers, or abbreviations associated with the user;
The password should be simple enough for the user to remember it.

6.3.1. The World Wide Web

The World Wide Web, or WWW, is a service through which network users gain access to information resources stored on computers in different parts of the world. The basis of the WWW are Web pages and Web sites on which information is presented in the form of hypertext and hypermedia documents.

You have already repeatedly traveled around the World Wide Web using browsers, following hyperlinks; looked for answers to your questions using search engines using keywords.

Problem 1. The table shows queries to the search server. The symbol used to denote the logical OR operation in queries is |, and the symbol & is used to denote the logical AND operation.

Graphically depict the number of pages that the search engine will find for each request. Arrange the query numbers in descending order of the number of pages that the search engine will find for each query.

Solution. Let's display the results of query execution graphically using Euler circles:

Another search option the required document on the Internet, this is the use of the document's address.

The address of a document on the Internet - its URL (Uniform Resource Locator - universal resource locator) consists of the following parts:

protocol name with // signs at the end of the name;
Domain name servers with a / at the end of the name;
the full name of the file on the server where it is located.

Let's look at an example address (URL):

http:// fcior.edu.ru/card/701/algebraicheskie-uravneniya.html

The first part of the address is the protocol name. It defines the document type. The HTTP:// entry indicates that this is a Web page (HTTP - Hyper Text Transfer Protocol - hypertext file transfer protocol). For other types of documents, the protocols may be different.

The second part of the address is the domain name of the server on which the page is stored.

http:// fcior.edu.ru/ card/701/algebraicheskie-uravneniya.html

The third part of the address is the full name of the file, including the path to the file, i.e., all the directories that should be sequentially entered to open the required file.

http://fcior.edu.ru/ card/701/algebraicheskie-uravneniya.html

Problem 2. The ftp.net file located on the txt.org server is accessed via the http protocol. In the table, fragments of the file address are encoded with letters from A to J. Write down the address of the specified file on the Internet and the sequence of letters encoding this address.

Solution. The first part of the file address is the protocol name:

The second part of the address is the name of the server (the computer on which the file is located):

The third part of the address is the full name of the file on the computer:

Answer: http://txt.org/ftp.net, GVZHEDBA.

6.3.2. File archives

There are many file archives on the Internet - libraries of sorts that store files with software, graphics, music and other information.

Users can access files in file archives using both the HTTP protocol and the special FTP file transfer protocol (File Transfer Protocol). FTP allows you to connect to file archive servers, view the contents of directories, and download files from or to a server. If the file transfer was interrupted for some reason, the FTP protocol provides tools for resuming the file, which can be very convenient when transferring large files.

The file address on the file archive server includes the file access protocol, the server name, and the full file name. So, if the htm.exe file located on the com.edu server is accessed via the ftp protocol, then its address will be written as follows:

ftp://com.edu/htm.exe

Many files received via FTP are compressed, that is, reduced in size. Compressed files take up less disk space and are transferred faster over the network. The names of such files usually end with the extensions zip, arj, rar and others, depending on the type of archiver program in which they were created. After copying a compressed file, it should be unpacked, i.e., restored to its original form.

6.3.3. Email

Electronic mail (e-mail) is a system for exchanging messages (letters) between subscribers of computer networks. It has a number of advantages over regular mail, namely:

high speed of message forwarding;
the ability to send, in addition to text documents, attached files containing graphics, sound, etc.;
the ability to simultaneously send letters to several recipients at once.

Currently, e-mail (postal service) is one of the main Internet services. Any Internet user can create his own mailbox - a named area of disk memory on the mail server of his provider, where incoming and outgoing correspondence will be placed. The user who has registered his mailbox receives an email address that looks like:<имя_пользователя>@.

First part (<имя_пользователя>) is selected by the user; The second part (<имя_сервера>) is tightly connected to the server on which the user registered his mailbox. The separator between parts of the address is the @ symbol.

Below is an example email address:

The mail server periodically scans subscribers' mailboxes and sends outgoing correspondence over the network (Fig. 6.6).

Rice. 6.6.
Email operation scheme

Unlike other Internet services, email uses not one, but two protocols:

SMTP protocol (Simple Mail Transfer Protocol) - for sending mail;
POP3 protocol (Post Office Protocol 3 - post office protocol, version 3) - for receiving mail.

Since anyone has the right to send mail to anyone, the SMTP protocol does not require identification of the sender. The letter should be received by the person to whom it is addressed; This requires identification of the recipient (by login and password), which is provided by the POP3 protocol.

Users can view email messages either using special programs (mail clients) or through a Web interface.

Each of these methods has its own advantages and disadvantages. The advantage of email clients is that when using them there is no need for a constant connection to the Internet. The Internet is needed for a short time to download messages from the mail server to the user's computer. All user correspondence (both received and sent) is stored on this computer. The disadvantage of this method is that the mailbox can only be accessed from the computer on which the mail client configured for a specific user is installed.

When using the Web interface, work with e-mail is carried out using a browser in the window of which a special hypertext page of the postal service website is loaded. In this case, all user correspondence is stored in his mailbox on the mail service server. Messages can be accessed from any computer connected to the network, but to read correspondence in this case, you must have an Internet connection.

Currently, the most popular email clients are Microsoft Outlook Express (included in the standard distribution of the OS family Microsoft Windows) and Mozilla Trunderbird (Fig. 6.7).

Rice. 6.7.
Logos of the most common email clients - Microsoft Outlook Express and Mozilla Trunderbird

An example of a postal service is mail.ru, the largest email system in Russia.

6.3.4. Networked Collaborative Collaboration

Network users have the opportunity to take part in various forms of collective interaction - teleconferences, forums, chats, social networks.

Teleconference is a system for exchanging information on a specific topic between network users. It is not limited by time and can last for months and years. First in computer network The opening of a conference on a specific topic is announced. The teleconference receives its email address. Then you sign up to participate in this teleconference. After this, each user who subscribes to the conference receives all its materials in their mailbox. In turn, by sending a letter to the conference, the user knows that it will reach all its participants. Most conferences are regulated by moderators - participants whose responsibilities include reviewing messages and making decisions - to publish these messages (send out to all conference participants) or not.

To organize communication between website visitors, Web forums are organized. The forum offers a set of sections for discussion. Users registered on the site, sending their messages, can create topics within sections and conduct discussions within these topics. The message and all replies to it form a forum “thread”. Unregistered users receive the status of guests who can view forum threads, but do not have the right to participate in discussions. Compliance with the rules is monitored by moderators who have the right to edit, move and delete other people's messages in a certain section or topic.

Chat(English chat - chat) - a group communication service that involves exchanging messages over a computer network in real time. A characteristic feature is real-time communication, which distinguishes a chat from a forum.

Recently, so-called social networks have become widespread among Internet users - interactive multi-user Web sites, the content of which is filled by network participants themselves. Such sites are automated social environments that allow groups of users with common interests to communicate.

6.3.5. Netiquette

There are unspoken rules of behavior on the Internet, the so-called netiquette. Briefly, the essence of netiquette can be expressed in one phrase: “Respect your invisible partners on the Internet!”

Here are the basic rules of netiquette that it is advisable to adhere to in email correspondence, as well as when using other Internet services.

Identify yourself clearly.
Know and respect your recipient.
Please indicate the subject of the message.
Write competently and briefly; give a clear answer to the question posed.
In text messages, you can express emotions using small drawings called emoticons.
Do not ask for confirmation of receipt of a message unnecessarily.
Do not allow spam - meaningless, intrusive or rude messages addressed to another person or group of people.
Do not expect complete confidentiality of correspondence.

The most important

A document posted on the Internet has a URL. Users can access documents posted on Web sites using the HTTP protocol.

File archive is a storage on the Internet of files with software, graphics, music and other information. Access to file archives is possible via the FTP file transfer protocol.

Electronic mail (e-mail) is a system for exchanging messages (letters) between subscribers of computer networks.

The main forms of collective interaction are teleconferences, forums, chats, and social networks.

Login is a combination of characters that are associated with the user. Password is a combination of characters confirming that the login owner intends to use the login.

Questions and tasks