File archives file archive servers. Archive (computer science)

Nowadays, when popularity World Wide The Web is quite large, the amount of traffic transmitted over Internet networks according to the FTP protocol, it nevertheless ranks first, slightly ahead of the volume of traffic according to HTTP protocol. In this light, organizing file archives within the framework of TCP/IP technology is an extremely urgent task.

Archives are used to solve different tasks, however, the most popular on the Internet are free available archives or such archives, access to which is authorized by an anonymous user ID. Thus, these archives can be used as:

Free software collections; collections of programs for beta testing; collections of normative and regulatory documents; and so on.

An FTP archive can also be used as an archive of commercial software that is used in a company, only in this case such an archive should not allow anonymous access to the resources stored in it.

Often, the option of authorized FTP access is also used for messaging, i.e. as a means of communication. This usually happens when the email system does not work for one reason or another.

Currently, the entire system of interaction between FTP exchange components can be represented in the form of a diagram shown in Figure 4.1.

This diagram shows two important technological points: firstly, the archive can be accessed not only from a specialized client program, but also from a universal browser, for example Netscape Communicator or Microsoft Internet Explorer, and secondly, you can use the Archie program to search for information in FTP archives.

Rice. 4.1. Interaction diagram of FTP exchange components

It should be clearly understood that Archie and FTP are completely different technologies. In most cases, users access the Archie server from the Archie client, which is located on the same machine as the server, i.e. First, the user logs in via Telnet as an Archie user, and then uses a client program (usually launched as a shell) to access the Archie server.

FTP protocol ( File Transfer protocol)

FTP (File Transfer Protocol) is one of the oldest protocols on the Internet and is part of its standards. Data exchange in FTP takes place over a TCP channel. The exchange was built using client-server technology. Figure 4.2 shows the protocol model.

Rice. 4.2. Protocol model

IN FTP connection initiated by the user protocol interpreter. The exchange is controlled via a control channel in the TELNET protocol standard. FTP commands are generated by the user's protocol interpreter and sent to the server. The server's responses are also sent to the user via the control channel. IN general case the user has the opportunity to establish contact with the server's protocol interpreter and by means other than the user's interpreter.

FTP commands define the parameters of the data transfer channel and the transfer process itself. They also determine the nature of work with remote and local file systems.

The control session initializes the data link. When organizing a data transmission channel, the sequence of actions is different, different from organizing a control channel. In this case, the server initiates data exchange in accordance with the parameters agreed upon in the management session.

The data channel is established for the same host as the control channel through which the data channel is configured. The data channel can be used for both receiving and transmitting data.

It is possible that data may be transferred to a third machine. In this case, the user organizes a control channel with two servers and organizes a direct data channel between them. Control commands go through the user, and data directly between servers (Figure 4.3).

The control channel must be open when transferring data between machines. If it is closed, data transmission stops.

Rice. 4.3. Connection with two different servers and transferring data between them

Communication modes

The protocol places great emphasis on in various ways data exchange between machines of different architectures. Indeed, there is so much on the Internet, from personal computers and Macs to supercomputers. They all have different word lengths and many different order bits in a word. In addition, different file systems work with different data organization, which is expressed in the concept of access method.

In general, from an FTP point of view, the exchange can be stream or block, with or without encoding in intermediate formats, text or binary. At text exchange all data is converted to ASCII and transmitted over the network in this form. The only exception is IBM mainframe data, which is sent to EBCDIC by default if both communicating machines are IBM. Binary data is transmitted as a sequence of bits or undergoes certain transformations during the control session. Typically, with streaming data transfer, one data file is transferred in one session, and with the block method, several files can be transferred in one session.

Having described in general outline exchange protocol, you can go to the description of exchange tools using the FTP protocol. For almost any platform and operating environment There are both servers and clients. Below are described standard server and a client for Unix-like systems.

Software for accessing FTP archives

To work with Ftp archives you need the following: software: server, client and search program. The server provides access to archive resources from anywhere on the network, the client provides user access to any archive on the network, and search system provides navigation throughout the entire network of archives.

In different operating systems these Ftp exchange components vary in both form and capabilities, but some general principles In addition, there are still interface-oriented programs command line, remain largely unchanged across different operating environments.

Protocol server - ftpd program

The ftpd command is designed to service requests for information exchange via the FTP protocol. The server usually starts when the computer boots. The syntax for starting the server is as follows:

ftpd [-d] [-1] [-t timeout] d - debugging option; 1 - automatic user identification option; t is the time of passive waiting for user commands.

Each server has its own description of commands, which can be obtained using the help command. Automatic user identification is carried out using the /etc/passwd file. The user password must not be empty.

Exists special file, which contains prohibited users, i.e. those for whom service via the FTP protocol is prohibited. You can enter the archive using an anonymous or ftp user ID. In this case, the server takes measures to restrict access to computer resources for given user. Typically, a special ftp directory is created for such users, in which the bin, etc and pub directories are located. The bin directory contains the commands allowed for use, and the pub directory contains the actual files themselves. The etc directory is not visible to the user and contains user identification files.

File sharing program - ftp

FTP is a user interface for exchanging files using the protocol of the same name. The program establishes a control channel with a remote server and waits for user commands. The remote server ID is specified either as a program argument or in the open interface command.

If the ftp command is running on a user and is waiting for user commands, the "ftp>" prompt is displayed on the screen.

Command syntax:

ftp [-v][-d][-i][-n] v - suppresses server responses and data transfer statistics; n - controls the user identification mode. If this switch is specified, the .netrc file is checked first; i - disables file transfer confirmations when copying files in bulk; d - turns on debugging mode; g - disables name transfer transparency.

Within this course there is no way to list everything ftp commands, so we will focus only on the most necessary ones.

The first such command is open command. This command opens a session with the remote server:

ftp>open polyn.net.kiae.su

After issuing such a command, user identification requests will follow. You can also register a user by user command:

ftp> user anonymous

IN in this example the user does not have special access rights to remote server and therefore registers as anonymous. In response to the identification request, in this case you should enter your mailing address. Usually it is enough to enter something similar to a postal address to gain access to archive resources, but there are also meticulous servers that check the presence of such an address, so it is better not to deceive anyone and register honestly.

The next most important commands are the cd and ls (dir) commands. The purpose of these commands is quite transparent and understandable to all users - navigation through the file system tree and viewing the contents of directories. Here it is recommended to use the ls command with additional parameters:

In this case, the user can receive a multi-column report indicating file types. However, not all servers work with this combination.

Since two machines are involved in the transfer and reception process, in addition to navigation in the remote file system, navigation in the local file system is also needed. The lcd (local cd) command is used for this purpose. In addition, the user can issue any local shell command if he precedes it with the "!" character:

This command will display the name of the current directory on local machine.

And finally, the most important commands are get, put, mget, mput and bin. The get and put commands can accept or transfer one file:

ftp> get README.TXT

The mget, mput commands are designed to receive/transmit a set of files:

ftp> mget *.gz

The example shows that in the latter case the “*” mask is used. Typically, when transferring groups of files, confirmation is requested for each file. To avoid this, issue the prompt command before sending/receiving. The latter switches the confirmation request mode and when reuse This command restores the confirmation request status. Another useful command is the hash command:

The "#" symbol can be replaced with any other one. When working on slow lines or when transmitting large files after turning on the hash mode, the user has the opportunity to see the process of data transfer (the “#” sign is issued after the transfer of each block). The last thing you should pay attention to is the bin command. After issuing this command, by default, data will be transferred in binary data transfer mode. The latter is extremely important, because When transferring to ASCII, programs and archived data cannot be transferred. It is often useful to enable bin mode for character data with an arbitrary line length, such as postscript (*.ps) files, because in ASCII mode there is a limit on line length (usually 254 characters).

To exit ftp, use the quit command.

Search in FTP archives - Archie program

Currently, FTP access is provided from a variety of multiprotocol interfaces (for example, Mosaic or Netscape) or graphical FTP shells such as ftptool for X-Window. All of them are much more convenient and easier to use, but they also consume much more resources.

It is curious that there is an FTP server even for MS-DOS (NCSA Telbin package), not to mention multitasking environments. However, finding the right FTP server on the Internet is a complex and time-consuming task. To make it easier there is special remedy- Archie. Archie was developed at McGill University in Canada. Archie's job is to scan FTP archives to see if they contain the required files. You can work with Archie through a telnet session, through a local client, or via e-mail. To work via telnet, you should open a telnet session and enter the word “archie” in response to login:

telnet archie.mcgill.ca

After the "archie>" prompt appears, you should inquire about the server's capabilities by entering the "help" command.

When working through a local client, simply enter:

archie gnuplot.tar.gz

and in response they receive a list of archives that contain the file “gnuplot.tar.gz”. It should be taken into account that various modifications of clients (especially graphical ones) may differ significantly in syntax from each other.

>>Informatics: File archives

File archives

File archive servers.

Hundreds of thousands of Internet servers are file archive servers, storing hundreds of millions of files. File servers supported by many development companies software and manufacturers of computer hardware components and peripheral devices. The software hosted on such servers is freely distributed (freeware) or shareware, and therefore, by downloading a particular file, the user does not violate the law on copyright for software. Lately music archive servers that store albums and musical compositions popular performers in MP3 format.

File transfer protocols.

Access to files on file archive servers is possible both via HTTP and a special transfer protocol FTP files(File Transfer Protocol). The FTP protocol allows you not only to download files from remote file archive servers to a local computer, but also vice versa, transfer files (Upload) from a local computer to a remote Web server, for example, in the process of publishing a Web site. For example, to download the file file.exe stored in the pub folder from the file archive server ftp.server.com, you must specify the URL of this file. When specifying a file URL, the FTP protocol is written as follows: ftp://

As a result, the universal resource locator takes the form: ftp://ftp.server.com/pub/file.exe It consists of three parts:

ftp:// - access protocol;

ftp.server.com - Domain name file archive server;

/pub/file.exe - file path and file name.

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

Internet and therefore include file download managers. After activating the link to the file in the window that opens, you need to specify the folder on the local computer in which the file should be saved. The file download will begin, the process of which is displayed on the information panel (transfer speed, volume of downloaded and remaining parts of the file, etc.).

Specialized file download managers. However, it is more convenient to use specialized file download managers (for example, FlashGet) to work with file archives. Such managers allow you to increase download speed by splitting files into parts and simultaneous download all parts. In addition, they allow you to continue downloading a file after the connection to the server is broken, contain a file search tool for other file archive servers, allow archive files in the process of downloading them, etc. The user is provided in numerical and graphical form detailed information about the file download process (current and average speed

downloads, download completion percentage, estimated download time, etc.). Specialized file download managers are integrated into browsers and when you activate a link to a file in the browser window, they begin the process of downloading it using the download manager.

FTP clients. FTP servers are servers with which files can be exchanged using the FTP protocol. FTP servers, according to their functional purpose, can be both file archive servers and Web servers on which Web sites are hosted. Files are downloaded from file archive servers to local computer , and vice versa, files are transferred to Web servers (Upload) from the local computer in the process of publishing Web sites. File exchange (downloading and transferring) with file archive servers and Web servers is carried out using specialized programs - FTP clients (for example, the FTP client is included in file manager). Access to file archive servers to download files to your local computer is usually anonymous and does not require a username and password. On the contrary, accessing Web servers to transfer files to a remote server during the process of publishing a Web site requires user authentication, that is, entering a user name and password. The FTP client includes a Site Manager, which allows you to create a list of servers with which you plan to work. Presents the directories of local and remote computers in a user-friendly form, ensures that the file continues to download after the connection is lost, etc. During the file transfer process, it displays necessary information: percentage of transferred file size, transfer speed, remaining time, etc.

Off-line browsers.

For fast loading Web sites for the purpose of further leisurely browsing in offline mode special programs are used - off-line browsers. Off-line browsers (for example, Offline Explorer) allow you to download entire Web sites or individual parts of a site to your local computer. The user can set the required “depth” of loading a Web site (the number of subdirectories), downloading multimedia files associated with pages, downloading Web pages from other Web servers via hyperlinks, etc. It is possible to continue loading the site after disconnecting and updating previously downloaded sites.

Computer Science and ICT: Textbook for 10th grade. N.D. Ugrinovich

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File archive servers. Hundreds of thousands of Internet servers are file archive servers, storing hundreds of millions of files. File servers are supported by many software companies and manufacturers of computer hardware components and peripherals. The software hosted on such servers is freely distributed (freeware) or shareware, and therefore, by downloading a particular file, the user does not violate the law on copyright for software.

Recently, music archive servers that store albums and musical compositions of popular artists in MP3 format have become widespread.

File transfer protocols. 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 (Download) from remote file archive servers to a local computer, but also, conversely, to transfer files (Upload) from a local computer to a remote Web server, for example, during the process of publishing a Web site.

For example, to download the file file.exe stored in the pub folder from the file archive server ftp.server.com, you must specify the URL of this file. When specifying a file URL, the FTP protocol is written as follows: ftp://.

As a result, the universal resource locator takes the form: ftp://ftp.server.com/pub/file.exe and consists of three parts:

ftp:// - access protocol;

ftp.server.com - domain name of the file archive server;

/pub/file.exe - file path and file name.

Uploading files using a browser. For the convenience of users, many file archive servers (freeware.ru, www.freesoft.ru, etc.) 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.

After activating the link to the file in the window that opens, you need to specify the folder on the local computer in which the file should be saved. The file download will begin, the process of which is displayed on the information panel (transfer speed, size of the downloaded and remaining part of the file, etc.).

Specialized file download managers. However, it is more convenient to use specialized file download managers (for example, ctmeuiGet) to work with file archives. Such managers allow you to increase download speed by splitting files into parts and downloading all parts at the same time. In addition, they allow you to continue downloading a file after the connection to the server is broken, contain a tool for searching for a file on other file archive servers, allow you to archive files while they are being downloaded, etc.

The user is provided with detailed information in numerical and graphical form about the process of downloading a file (current and average download speed, percentage of download completion, estimated download time, etc.).

Specialized file download managers are integrated into browsers and when you activate a link to a file in the browser window, they begin the process of downloading it using the download manager.

Access to file archive servers to download files to your local computer is usually anonymous and does not require a username and password. On the other hand, access to Web servers for the purpose of transferring files to a remote server during the process of publishing a Web site requires user identification, i.e. entering your username and password.

FTP client includes Site Manager, allowing you to create a list of servers with which you plan to work. Presents the local and remote computer, ensures that the file continues to download after the connection is lost, etc. During the file transfer process, the necessary information is displayed: the percentage of the transferred file volume, the transfer speed, the remaining time, etc.

Offline browsers. To quickly load Web sites for further leisurely viewing in offline mode, special programs are used - offline browsers.

Offline browsers (for example, Offline Explorer) allow you to download entire Web sites or individual parts of a site to your local computer. The user can set the required “depth” of loading a Web site (the number of subdirectories), downloading multimedia files associated with pages, downloading Web pages from other Web servers via hyperlinks, etc. It is possible to continue loading a site after the connection is disconnected and update previously downloaded sites.

Program repositories for the Linux operating system. In the operating system Linux components The system itself and applications are stored in the form of “packages” (rpm extension), which each user can download and install in their own version of the system. In short, each user composes his own operating system Linux system and its applications based on your needs and preferences, using a set of packages in the repositories.

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?
3. What is the advantage of downloading files using specialized managers downloads before downloading files using browsers?
4. Compare download managers and FTP clients. What is their difference?
5. In what cases is it advisable to use offline browsers?

Tasks for independent completion

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

Nowadays, when the popularity of World Wide Web is quite large, the volume of traffic transmitted over the Internet via the FTP protocol nevertheless occupies first place, slightly ahead of the volume of traffic via the HTTP protocol. In this light, organizing file archives within the framework of TCP/IP technology is an extremely urgent task.

Archives are used to solve various problems, but the most popular on the Internet are freely accessible archives or archives that can be accessed using an anonymous user ID. Thus, these archives can be used as:

collections of free software;
collections of programs for beta testing;
collections of normative and regulatory documents;
and so on.

An FTP archive can also be used as an archive of commercial software that is used in a company, only in this case such an archive should not allow anonymous access to the resources stored in it.

Often, the option of authorized FTP access is also used for messaging, i.e. as a means of communication. This usually happens when the email system does not work for one reason or another.

Currently, the entire system of interaction between FTP exchange components can be represented in the form of a diagram shown in Figure 4.1.

This diagram shows two important technological points: firstly, the archive can be accessed not only from a specialized client program, but also from a universal browser, for example Netscape Communicator or Microsoft Internet Explorer, and secondly, to search for information in FTP archives, you can use the Archie program.

Rice. 4.1. Interaction diagram of FTP exchange components

FTP (File Transfer Protocol)

Rice. 4.2. Protocol model

In FTP, the connection is initiated by the user's protocol interpreter. The exchange is controlled via a control channel in the TELNET protocol standard. FTP commands are generated by the user's protocol interpreter and sent to the server. The server's responses are also sent to the user via the control channel. In general, the user has the ability to establish contact with the server's protocol interpreter and by means other than the user's interpreter.

FTP commands define the parameters of the data transfer channel and the transfer process itself. They also determine the nature of work with remote and local file systems.

The data channel is established for the same host as the control channel through which the data channel is configured. The data channel can be used for both receiving and transmitting data.

The control channel must be open when transferring data between machines. If it is closed, data transmission stops.

Rice. 4.3. Connecting to two different servers and transferring data between them

. Communication modes

The protocol places great emphasis on different ways of exchanging data between machines of different architectures. Indeed, there is everything on the Internet, from personal computers and Macs to supercomputers. They all have different word lengths and many different orders of bits in a word. In addition, different file systems work with different data organization, which is expressed in the concept of access method.

In general, from an FTP point of view, the exchange can be stream or block, with or without encoding in intermediate formats, text or binary. During text exchange, all data is converted to ASCII and transmitted over the network in this form. The only exception is IBM mainframe data, which is sent to EBCDIC by default if both communicating machines are IBM. Binary data is transmitted as a sequence of bits or undergoes certain transformations during the control session. Typically, with streaming data transfer, one data file is transferred in one session, and with the block method, several files can be transferred in one session.

Having described the exchange protocol in general terms, we can move on to a description of the means of exchange using the FTP protocol. There are both servers and clients for almost any platform and operating environment. The following describes the standard server and client of Unix-like systems.

Software for accessing FTP archives

To work with Ftp archives, you need the following software: server, client and search program. The server provides access to archive resources from anywhere on the network, the client provides user access to any archive on the network, and the search engine provides navigation throughout the entire network of archives.

These Ftp sharing components vary in both form and functionality across operating systems, but some general principles remain, and command line interface programs remain largely the same across operating environments.

Protocol server - ftpd program

The ftpd command is designed to service requests for information exchange via the FTP protocol. The server usually starts when the computer boots. The syntax for starting the server is as follows:

Ftpd [-d] [-1] [-t timeout]

d - debugging option;
1 - automatic user identification option;
t is the time of passive waiting for user commands.

There is a special file that contains banned users, i.e. those for whom service via the FTP protocol is prohibited. You can enter the archive using an anonymous or ftp user ID. In this case, the server takes measures to limit access to computer resources for this user. Typically, a special ftp directory is created for such users, in which the bin, etc and pub directories are located. The bin directory contains the commands allowed for use, and the pub directory contains the actual files themselves. The etc directory is not visible to the user and contains user identification files.

File sharing program - ftp

If the ftp command is running on a user and is waiting for user commands, the "ftp>" prompt is displayed on the screen.

Command syntax:

Ftp [-v][-d][-i][-n]

v - suppresses server responses and data transfer statistics;
n - controls the user identification mode. If this switch is specified, the .netrc file is checked first;
i - disables file transfer confirmations when copying files in bulk;
d - turns on debugging mode;
g - disables name transfer transparency.

Within the framework of this course, it is not possible to list all the ftp commands, so we will focus only on the most necessary ones.

The first such command is open command. This command opens a session with the remote server:

Ftp>open polyn.net.kiae.su

After issuing such a command, user identification requests will follow. You can also register a user by user command :

Ftp>user anonymous

In this example, the user does not have special access rights to the remote server and is therefore registered as anonymous. In this case, you should enter your mailing address in response to the identification request. Usually it is enough to enter something similar to a postal address to gain access to archive resources, but there are also meticulous servers that check the presence of such an address, so it is better not to deceive anyone and register honestly.

The next most important commands are cd commands And ls (dir). The purpose of these commands is quite transparent and understandable to all users - navigation through the file system tree and viewing the contents of directories. Here we recommend using the ls command with additional parameters when browsing directories:

Ftp>ls -FC

In this case, the user can receive a multi-column report indicating file types. However, not all servers work with this combination.

Ftp> !pwd

This command will display the name of the current directory on the local machine.

And finally, the most important are teams data reception/transmission get , put , mget , mput And bin. The get and put commands can accept or transfer one file:

Ftp>get README.TXT

The mget, mput commands are designed to receive/transmit a set of files:

Ftp> mget *.gz

The example shows that in the latter case the “*” mask is used. Typically, when transferring groups of files, confirmation is requested for each file. To avoid this, before receiving/transmitting, you should issue prompt command. The latter switches the confirmation request mode and when this command is used again, the confirmation request state is restored. Another useful command is hash command :

Ftp> hash #

The "#" symbol can be replaced with any other one. When working over slow lines or when transferring large files, after enabling the hash mode, the user has the opportunity to see the progress of data transfer (the "#" sign is issued after the transfer of each block). The last thing you should pay attention to is the bin command. After issuing this command, by default, data will be transferred in binary data transfer mode. The latter is extremely important, because When transferring to ASCII, programs and archived data cannot be transferred. It is often useful to enable bin mode for character data with an arbitrary line length, such as postscript (*.ps) files, because in ASCII mode there is a limit on line length (usually 254 characters).

To exit ftp you should run quit command .

Search in FTP archives - Archie program

It is curious that there is an FTP server even for MS-DOS (NCSA Telbin package), not to mention multitasking environments. However, finding the right FTP server on the Internet is a complex and time-consuming task. To alleviate it, there is a special remedy - Archie. Archie was developed at McGill University in Canada. Archie's job is to scan FTP archives to see if they contain the required files. You can work with Archie through a telnet session, through a local client, or via email. To work via telnet, you should open a telnet session and enter the word “archie” in response to login:

Telnet archie.mcgill.ca login: archie...... archie>

After the "archie>" prompt appears, you should inquire about the server's capabilities by entering the "help" command.

When working through a local client, simply enter:

Archie gnuplot.tar.gz

File archives are a file created using a special program called an archiver, and containing from one to several files and/or directories (folders) in packed form.

Historical aspect

Such archives were used most actively during the use of floppy disks, since file archives make it possible to compress some types of files (excluding graphics and video) in order to place them on a small diskette. With their disappearance, the use of archives mainly moved to the Internet, where they continue to be used mainly in file sharing services and on ftp servers.

Classification of archives

Highlight the following types file archives:

regular - in one archive file there are several files and/or folders compressed by some method;
self-extracting - are executable files with extension .exe; when starting, you only need to specify the unpacking path, the program itself will do the rest;
multi-volume - includes a number of parts of the archive, which, in addition to their own extension, can have an additional extension showing the part number: part01...;
continuous - archives with the highest possible degree of compression, in which all files and folders form a single whole; unpacking one file (folder) is impossible;
password protected - archives that require a password to be opened.

File archive extensions

Each file has specific extensions. File archives are no exception. These are, first of all, zip, rar, 7z - the most popular extensions used in the operating system Windows system. Such extensions in the GNU/Linux OS can be found very rarely, mainly from those users who have recently switched to using this OS after Windows. Here the most common archives are gz, bz2, xz. Working with these extensions is usually accompanied by tar compression, as a result general expansion looks like tar.gz, tar.bz2, tar.xz. Often tar.bz2 and tar.xz are more efficient in compression than zip. These formats are not common in Windows OS, but can be successfully used there in all common archivers.

The best compression level in the most common Windows OS is 7z, but tests show its slight superiority over other file archive extensions. Working with zip in Windows is available after installing the system, just like in Mac OS X; most GNU/Linux distributions also work with this archive out of the box, since archivers that support most common file archive formats are installed along with the distribution.

Working with file archives

File archives assume the presence special programs, which could efficiently create and unpack them. It should be noted that most archivers for Windows OS create corresponding items in context menu, which is called by right-clicking. We will look at file archives for desktop computers, but there are also ones for gadgets that can be found in the appropriate stores.

Let's look at the most common file archive programs.

WinZip

By default, it saves files in zip, but you can save in other formats. Using this archiver you can compress mp3 files and jpeg files up to 25% without losing quality. The compression method is selected automatically. There are functions for printing files that are compressed into a given archive, checking them with an antivirus, and others. The latest versions of the application support opening 7z, rar and zipx files.

According to the developers, WinZip provides protection using bank-grade encryption. In addition, the latest versions have the ability to connect to clouds.

In this program, new MS Office document formats can be opened as file archives: docx, xlsx, etc., as well as formats corresponding international standard O.D.F.

As the developers say, reducing the size graphic files occurs due to the fact that some formats are replaced by others.

In case of accidental deletion, copying, renaming, files can be restored.

WinRAR

All over the world, zip archives lead in popularity, but Russia goes its own way, and our most popular archiver is WinRAR. This archiver has a command line mode (this is what is used in GNU/Linux environments), the latest versions have also learned to effectively compress media content. It has its own support for a variety of formats, including both the popular rar and zip, as well as the less popular gz, tar, bz2, lzma and others.

In WinRAR you can select the compression time, but it must be taken into account that stronger compression will lead to more time spent on the archiving process. In the settings of this archiver, you can set a low priority, which will increase the loading and unpacking time, but will also reduce the load on the processor, or you can use all processor cores, which will lead to a higher load on them, but will reduce the time of creating an archive or unpacking.

PeaZip

This program is cross-platform and can be installed on many operating systems. Capable of opening more than 180 file archive formats. This is probably a record. It supports simultaneous work with several archives. IN latest versions support for opening zipx, rar, including its fifth version is provided.

This application also supports data encryption, it has the ability to convert a disk into a file NTFS system, it is possible to create keys, backup copies files. The program is released for both 32-bit and 64-bit platforms.

7-zip

This archiver creates native 7z formats, although a number of others are supported, including popular formats on Windows and POSIX systems, including GNU/Linux and Mac OS X. Among other things, it allows you to open rar archives, deb, which contain binary files installers of programs in GNU/Linux OS. According to the developers, the compression rate is 30-70% higher than WinRAR, and 2-10% higher than WinZip.

Unlike the first two archivers, who want users to receive money for using them, the last two belong to open source programs and are free. In 2007, this archiver was recognized as the best by the SourceForge.net project.

Encryption is implemented using the algorithm AES-256 for 7z and zip file archives. Archives packed using the LZMA method are unpacked literally on the fly.

Like PeaZip, there are applications for both 32- and 64-bit platforms.

File archives on the Internet

Many servers in World Wide Web contain them. Internet servers containing file archives are called ftp servers. Until recently, almost everything could be found on these servers - from music to toys and programs for various systems. The fight against piracy in our country has somewhat crippled this segment, and now it mainly houses free products.

FTP servers host GNU/Linux OS repositories, so every user of these systems has the opportunity free installation programs signed digital keys, which eliminates the possibility of malicious code penetrating the user’s computer, which is why these systems are famous for their absence of viruses.

Ftp servers can be viewed from any browser; there are special clients for them.

Data exchange from the ftp server with users occurs over a TCP channel. Exchange management is regulated in the TELNET protocol standard.

Using ftp protocol it is possible not only to download files to your local computer, but also to transfer them to

File archive system by using ftp server Any interested person can.

The server data ensures that file archives are provided and received by both anonymous users and authorized users. Most ftp servers are anonymous.

Despite the described advantages, ftp servers are not without disadvantages. A huge part of the file archives in them are presented without description, and you can only guess what is in front of you through a targeted search.

File transfer can be carried out in text or binary mode. When wrong choice the file may become damaged.

No via ftp servers universal search. There are several solutions, but they are not all universal.

The most common among them is the Archie service. Archie servers are heavily loaded and only work with anonymous ftp. However, the server data is decentralized, the search is carried out using a not entirely clear algorithm, as a result of which, if you go through all the servers (and there are about a dozen of them), you may not find it the information you are looking for. In addition, you must be able to create a search template when using this service.

In addition to using the ftp protocol, the http protocol can be used to access file archives.

File archives represent not only open source software, you can also find various texts, demo versions of proprietary programs and much more.

Finally

Thus, file archives are a necessary thing in order to transmit a large amount of information in a compressed form. This archives can be used locally - on separate computers, and in global network Internet through the use of special ftp and http servers. The most common programs for creating archives and unpacking them are WinRAR, WinZip, PeaZip, 7-zip. The last two programs are free and can be used for free. Most archivers support all the most common archive formats.