Archiving is the compression of one or more files to save memory and placing the compressed data in a single archive file. Data archiving is the reduction of the physical size of the files in which data is stored, without significant information loss.

Archiving is performed in case:

§ the need to create backup copies of the most important files;

§ the need to free up disk space;

§ the need to transfer files by E-mail.

An archive file is a set of several files (one file) placed in a compressed form into a single file, from which they can be extracted in their original form, if necessary. The archive file contains a table of contents that lets you know what files are in the archive.

File name;

§ file size on disk and in the archive;

§ about the location of the file on the disk;

§ date and time of the last modification of the file;

§ Cyclic control code for the file used to check the integrity of the archive;

§ compression ratio.

Any archive has its own compression ratio scale. The most common gradation of compression methods is:

§ without compression (corresponds to the usual copying of files into an archive without compression);

§ high-speed;

§ fastest (characterized by the fastest, but least dense compression);

§ usual;

§ good;

§ maximum (maximum possible compression is also the slowest compression method).

The compression ratio depends on:

used archiver;

compression method;

source file type.

The compression ratio is characterized by the compression ratio:

where V c is the size of the compressed file;

V and - the volume of the source file.

Different types of files are compressed in different ways. For example, the compression ratio of text documents is significantly higher than that of graphic documents.

Archivers are used to compress files.

Archivers are programs (a set of programs) that compress and restore compressed files in their original form.

The process of compressing files is called archiving. The process of recovering compressed files is by unzipping.

Modern archivers differ in the algorithms used, the speed of work, the compression ratio (WinZip 9.0, WinAce 2.5, PowerArchiver 2003 v. 8.70, 7Zip 3.13, WinRAR 3.30, WinRAR 3.70 RU).

WinRAR archiver

WinRAR is a 32-bit version of the RAR archiver for Windows. It is a powerful tool for creating and managing archives. There are several versions of RAR for different operating systems: Windows, Linux, UNIX, DOS, OS / 2, etc.

There are two versions of RAR for Windows:

§ version with graphical user interface - WinRAR.EXE;

§ console version RAR.EXE command line console (text mode) version - Rar.exe

WinRAR features:

§ allows you to unpack archives CAB, ARJ, LZH, TAR, GZ, ACE, UUE, BZ2, JAR, ISO, and provides data archiving in ZIP and RAR formats;

§ provides full support for ZIP and RAR archives;

§ has special algorithms optimized for text and graphics. For multimedia, compression can only be used with RAR formats;

§ Supports drag & drop technology;

§ has a command line interface;

§ can perform continuous archiving, which provides a higher compression ratio than conventional compression methods, especially when packing a large number of small files of the same type;

§ provides support for multivolume archives, that is, it splits the archive into several volumes (for example, to write a large archive to disks). Volume expansion: RAR, R01, R02, etc. In a self-extracting archive, the first volume has the EXE extension;

§ creates self-extracting archives (SFX), regular and multivolume archives, ensures their protection with passwords;

§ provides recovery of physically damaged archives;

§ has recovery tools that allow you to recover missing parts of a multivolume archive;

§ supports UNICODE in filenames;

§ The Wizard mode is intended for beginners, with the help of which you can easily carry out all operations with archives.

WinRAR has other additional features as well. WinRAR is capable of creating an archive in two different formats: RAR and ZIP. Let's take a look at the advantages of each format.

ZIP archive

The main advantage of the ZIP format is its popularity. For example, most archives on the Internet are ZIP archives. Therefore, it is best to submit an email attachment in ZIP format. You can also send a self-extracting archive. This archive is a bit large, but can be extracted without external programs. Another advantage of ZIP is speed. ZIP archive is usually faster than RAR archive.

Archive in RAR format

The RAR format provides significantly better compression than ZIP in most cases. In addition, the RAR format provides support for multivolume archives, has tools for recovering damaged files, archives files of almost unlimited sizes. It should be noted that when working in the FAT32 file system, archives can only reach 4 gigabytes. Working with large archive sizes is supported only in the NTFS file system.

Microsoft Backup archiving program (backup).

The program is launched: Start - Programs - Standard - Service - Data archiving. This will open the Backup and Restore Wizard in normal mode. From this mode, you can switch to advanced mode to work with the backup wizard, recovery wizard and OS disaster recovery wizard.

The archiving program allows you to protect data from accidental loss in the event that a hardware failure or media failure occurs in the system. With Backup, you can back up your data to your hard drive and then create an archive on another storage medium. The archive medium can be a logical disk or a separate device (removable disk).

The backup program creates a snapshot of the volume, which is an exact copy of the contents of the disk at a specific point in time, including open files used by the system. During the execution of the backup program, the user can continue to work with the OS without the risk of data loss.

The archiving program provides the following features:

1. Backing up selected files and folders in case of hard disk failure or accidental deletion of files (you can back up to a hard disk or removable disk, etc.). Backup restores archived files and folders to your hard drive.

2. Archiving system state data. The program allows you to back up copies of important system components such as the registry, boot files, and the directory service database. The backup utility allows you to restore copies of important system components such as the registry, boot files, and the directory service database.

Topic 1.3: System Software

Topic 1.4: Service software and the basics of algorithmization

Introduction to Economic Informatics

1.4. PC service software and algorithms basics

1.4.1. Service software (standard and utility programs, data archiving, anti-virus programs)

1.4.1.2. Data archiving programs

Archiving is the compression of one or more files to save memory and placing the compressed data in a single archive file. Data archiving is the reduction of the physical size of the files in which data is stored, without significant information loss.

Archiving is carried out in the following cases:

• when you need to back up your most valuable files;
• when you need to free up disk space;
• when it is necessary to transfer files by E-mail.

  An archive file is a set of several files (one file) placed in a compressed form into a single file, from which they can be extracted in their original form, if necessary. The archive file contains a table of contents that lets you know what files are in the archive.

  • file name;
  • file size on disk and in the archive;
  • information about the location of the file on the disk;
  • date and time of the last modification of the file;
  • cyclic control code for the file used to check the integrity of the archive;
  • compression ratio.

  Any of the archives has its own compression ratio scale. Most often you can find the following gradation of compression methods:

  1. Uncompressed (corresponds to the usual copying of files into an archive without compression).
  2. High-speed.
  3. Fast (characterized by the fastest, but least dense compression).
  4. Usual.
  5. Good.
  6. Maximum (the highest possible compression is also the slowest compression method).

  Best of all archived graphic files in .bmp format, MS Office documents and Web pages.

  What are archivers?

  Archivers are programs (a set of programs) that compress and restore compressed files in their original form. The process of compressing files is called archiving. The process of recovering compressed files is by unzipping. Modern archivers differ in the algorithms used, the speed of work, the compression ratio (WinZip 9.0, WinAce 2.5, PowerArchiver 2003 v.8.70, 7Zip 3.13, WinRAR 3.30, WinRAR 3.70 RU).

  Other names for archivers: utilities - packers, programs - packers, utilities that allow you to put copies of files in a compressed form in an archive file.

  There are archivers in MS DOS, but they work only in the command line mode. These are PKZIP and PKUNZIP programs, ARJ archiver program. Modern archivers provide a graphical user interface and retained the command line. Currently, the best archiver for Windows is WinRAR.

  WinRAR archiver

  WinRAR is a 32-bit version of the RAR archiver for Windows. It is a powerful tool for creating and managing archives. There are several versions of RAR for different operating systems: Windows, Linux, UNIX, DOS, OS / 2, etc.

  There are two versions of RAR for Windows:
  

  • version with a graphical user interface - WinRAR.EXE;
  • Console version RAR.EXE command line console (text mode) version is Rar.exe.

  
  Figure: 1.

  WinRAR features:

  1. Allows you to unpack archives CAB, ARJ, LZH, TAR, GZ, ACE, UUE, BZ2, JAR, ISO, and provides data archiving in ZIP and RAR formats.
  2. Provides full support for ZIP and RAR archives.
  3. Has special algorithms optimized for text and graphics. For multimedia, compression can only be used with RAR formats.
  4. Supports drag & drop technology.
  5. Has a command line interface.
  6. Can perform continuous archiving, which provides a higher compression ratio than conventional compression methods, especially when packing large numbers of small files of the same type.
  7. Provides support for multivolume archives, that is, it splits the archive into several volumes (for example, to write a large archive to disks). Volume expansion: RAR, R01, R02, etc. In a self-extracting archive, the first volume has the EXE extension.
  8. Creates self-extracting archives (SFX), regular and multi-volume archives, provides password protection.
  9. Provides recovery of physically damaged archives.
  10. Has recovery tools that allow you to recover missing parts of a multivolume archive.
  11. Supports UNICODE in filenames.
  12. For beginners, the Wizard mode is intended, with which you can easily carry out all operations with archives.

  WinRAR has other additional features as well. WinRAR is capable of creating an archive in two different formats: RAR and ZIP.

  Let's take a look at the advantages of each format.

  ZIP archive

  The main advantage of the ZIP format is its popularity. For example, most archives on the Internet are ZIP archives. Therefore, it is best to submit an email attachment in ZIP format. You can also send a self-extracting archive. This archive is a bit large, but can be extracted without external programs. Another advantage of ZIP is speed. ZIP archive is usually faster than RAR archive.

  Archive in RAR format

  the RAR format in most cases provides significantly better compression than ZIP. In addition, the RAR format provides support for multivolume archives, has tools for recovering damaged files, archives files of almost unlimited sizes. It should be noted that when working in the FAT32 file system, archives can only reach 4 gigabytes. Working with large archive sizes is supported only in the NTFS file system.

  Microsoft Backup Archiving Program (backup)

  The program is launched: Start - Programs - Standard - Service - Data archiving. The Backup and Restore Wizard will open as usual. From this mode, you can switch to advanced mode to work with the Backup Wizard, Recovery Wizard, and OS Disaster Recovery Wizard.

  
  Figure: 2.

  The archiving program allows you to protect data from accidental loss in the event that a hardware failure or media failure occurs in the system. With Backup, you can back up your data to your hard drive and then create an archive on another storage medium. The archive medium can be a logical disk or a separate device (removable disk).

  The backup program creates a snapshot of the volume, which is an exact copy of the contents of the disk at a specific point in time, including open files used by the system. During the execution of the backup program, the user can continue to work with the OS without the risk of data loss.

  The archiving program provides the following features:

  1. Back up selected files and folders in case of hard drive failure or accidental file deletion (you can back up to a hard drive or removable drive, etc.). Backup restores archived files and folders to your hard drive.
  2. Archiving system state data. The program allows you to back up copies of important system components such as the registry, boot files, and the directory service database. The backup utility allows you to restore copies of important system components such as the registry, boot files, and the directory service database.

computer file compression archive

A distinction should be made between the archiving program itself, the archive format and the compression methods. Even the same compression method may have implementation options. For example, there are over a dozen archiving programs that can create archives in ZIP format. In turn, data in ZIP format can be compressed using various methods: Deflate, Deflate64, BZip2. The Deflate method has several implementations with varying speed and compression ratio. With this method, the 7-zip archiver allows you to create archives in ZIP and 7Z format.

Usually archivers can create archives in their own exclusive format using their original methods. For example, the RAR archiver allows you to create RAR archives. The archive format and compression methods are the main advantages of this or that archiver.

In the simplest case, the archiver only allows you to pack or unpack one file. In addition to the actual data compression, modern archivers provide some additional functions. There are several main ones:

Compression of some files and entire directories;

Creation of self-extracting (SFX) archives. That is, an archiver program is not required to unpack the archive;

Changing the contents of the archive;

Encryption of archive contents;

Information for recovering an archive in case of partial damage and the ability to recover damaged archives;

Splitting the archive into several parts or volumes;

Console version of the program for working from the command line;

Graphical (GUI) version of the program.

It should be noted that, despite the formal presence, the implementation of each additional function can be performed at a completely different level.

In addition to differences in functionality, archivers can be divided into two groups: asymmetric and symmetric. Asymmetric archivers require significantly less time and memory for the decompression operation than for the packing operation. This allows you to quickly retrieve the contents of the archive on low-power computers. Symmetric archivers require the same amount of RAM and time for packing and unpacking operations. The use of such archivers on a wide range of computers or for online access to the contents of the archive is limited. The well-known RAR archiver uses the asymmetric dictionary compression method as the main one, and for texts it can use the symmetric PPM method. Thus, unpacking RAR archives compressed with the maximum compression ratio may not be possible on computers with limited RAM. All or nearly all of the advanced high compression ratio archivers are symmetric.

Despite the very modest data on the prevalence of archivers, there are many of them. Most of them belong to the category of experimental and archivers with limited functionality. However, each of them allows you to perform the actual data compression procedure.

Ramotrim the most popular archiving programs:

1. WinRAR

Version 2.90 Final

Supported platforms: Windows, Linux, BeOS and DOS-32

WinRAR is a 32-bit version of the RAR archiver for Windows. Apart from full RAR and ZIP support, WinRAR 2.90 can unpack UUE, GZ, TAR, ARJ, LZH, ACE, CAB, BZIP2, JAR (Java ARchive) and ACE 2.0 archives. WinRAR has an original compression algorithm with high compression ratios, especially on executable files, large text files, etc. The number of compressed files included in the archive is not limited.

There is support for ZIP archives; graphical interactive interface along with command line. WinRAR provides the ability to create solid archives, which benefits from archiving a large number of files.

It is possible to create self-extracting (SFX), regular and multivolume archives. Available locking, encryption, file order list, volume labels.

There are also additional functions, such as encryption, adding archived comments, logging errors, etc.

2. WinZip

Version v8.1

One of the most popular programs on the Internet. The ZIP algorithm itself is freely used in dozens, if not hundreds of programs, and, nevertheless, for most Windows users, it is WinZIP that serves as the standard program for working with archives. WinZip is easy to use, has long name support, and is optimized for Windows environments.

WinZIP can view and extract files from other less common archive formats such as ARJ, LZH, ARC, TAR, TAZ, TGZ, Z, GZ, CAB, UUE, XXE, UU, B64, HQX, BHX. There are functions for installing programs, screen themes and screen savers from archives, performing many operations through step-by-step Wizards, compressing and sending files by mail, checking the contents of archives with an external antivirus, managing bookmarks of selected archive directories, the ability to integrate with Windows Explorer is supported (adding commands to context menus) There are separate utilities for working from the command line, integration with popular Internet browsers, and creating self-extracting archives.

WinZip has a very convenient auto-installation feature for software distributed as Zip files.

For easy zipping / unzipping of files, WinZip offers the WinZip Wizard. It is possible to organize files into "Favorite" folders (Favorite Zip Folders). WinZip allows you to organize your Zip files into a single “sheet,” which makes it easier to combine and sort Zip files no matter where they are physically stored. The search function allows you to find any Zip files "lost" on your hard drive. It is possible to create self-extracting files. WinZip can be configured to work with most modern antivirus scanners.

3. WaveZip

Version 2.0

The program was developed as a tool for compressing large audio WAV-files that take up a lot of space.

WaveZIP is easy to use and allows you to quickly find, select and convert files. Drag-and-drop functionality from Windows Explorer is supported.

The program implements a special MUSICompress technology from Soundspace Audio. The compression is absolutely lossless, the algorithms are optimized specifically for the compression tasks of the WAV format (the average compression ratio, depending on the file type, reaches 30-60%).

4. WavPack

Version 3.92

Supported platforms: Win9x, WinNT, Mac

Console compressor specialized in audio compression. Provides lossless packing / decompression of 16/24-bit mono and stereo WAV files. WavPack delivers fast performance, 25-50% compression for pop music and slightly better compression for classical music and compositions with a wide dynamic range. The maximum attainable packing level is 87% (for periods of silence). A configurable lossy compression mode is provided (up to 67% with inaudible loss and up to 77% with noticeable noise), compression of "raw" audio files of unknown formats is possible, fast packing mode is supported, there is a WinAMP plugin for playing compressed WavPack files.

5. PowerArchiver

Version v7.02

Supported platforms: Win9x, WinNT

Powerful multi-format Windows GUI shell that allows you to work with archives in ZIP, RAR, CAB, ARJ, LHA, ACE, ARC, TAR, BZIP2, TAR.BZ2, GZ, BH, ZOO, XXE, UUE formats. In addition to standard operations, PowerArchiver can rename files in archives, install programs from them, scan content for viruses, convert archives from one format to another, protect them with a password, repair, create multivolume and self-extracting (SFX) archives. The program also allows you to view TXT, RTF, BMP, ICO, GIF, WMF, EMF and JPG files by its own means, print lists of archive files or export them in TXT and HTML formats. There are tools for managing the list of quick access to frequently used directories, changing the appearance of the button panel using skins, performing data backup operations using scripts, searching for program updates on the Internet, creating a separate archive for each compressed file.

PowerArchiver has a user-friendly Office 2000 style switchable interface with detailed help system and integrates with Windows Explorer, providing support for Drag & Drop operations and convenient context menus.

6. ZipMagic

Version 4.0

Supported platforms: Win9x, WinNT

Mijenix has released an updated version of its popular ZipMagic software. The purpose of the program is to provide the ability to work with archives as with ordinary disk folders. That is, all zip files on disks magically "turn" into regular directories. At the same time, neither Explorer, nor Norton Commander, nor any other program suspects that they are dealing with archives. The user can work with pseudo-folders: rename them, run and install programs, games from them, view, edit, copy, rename files, create and delete subdirectories, etc. ZipMagic will quietly perform compression / decompression operations, and significantly faster than most known zip packers.

The new version of the program adds support for most of the new archive formats and encodings. Among them: RC, ARJ, CAB, GZ, LHA / LZH, RAR, TAR, ZOO, UU / XXEncode and many others. At the same time, to work with files of these formats, you do not need the utilities that created them themselves. The ZipTools utility supplied with ZipMagic is designed to work with them. All of the above-mentioned file types are automatically associated in the registry with this utility and, of course, are opened with it.

ZipTools is a kind of Explorer, with which you can perform all the standard functions inherent in file managers (copying, transferring, renaming files, Drag & Drop support, customizing panels, sorting, multiple windows, etc.), as well as specific functions such as UU -encoding, converting to ZIP, formatting disks, searching for files / computers and the like. In addition, ZipTools allows you to quickly view over 60 file / document formats, including multimedia, without leaving the program.

ZipMagic also includes the ZipWizard utility, an automated tool for creating / converting / unpacking archives for beginners, providing a step-by-step simplified interface for performing standard operations.

In addition, the program comes with special zip-plugins for browsers and e-mail. The first - ZipSurfer - is designed to work in Netscape Navigator, Netscape Communicator and Internet Explorer and allows you to unpack, view archives freshly downloaded from the Internet, install programs from them and perform other operations with archives without leaving your browser (something similar is available in the famous WinZip ).

The second plugin, ZipMail, is an add-on to programs such as Eudora Light, Eudora Pro, Microsoft Exchange, Outlook 97, and Outlook 98.

In ZipMagic options, you can change a huge number of parameters, among which there are special Windows NT options. You can define the program autorun options, set the compression ratio with which files will be compressed when creating an archive-folder, set the program cache size, hotkeys, select disks for which ZipMagic functions will work, define the time to enable / disable program functions. You can also define which applications will still treat zip archives as files rather than directories, such as backup and disk utilities.

The advantages and disadvantages of the described programs can be presented in the form of graphical drawings.

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Ministry of Agriculture of the Russian Federation

Transbaikal Agrarian Institute - branch of the Federal State Budgetary Educational Institution of Higher Education

Irkutsk State University named after A.A. Ezhevsky "

On the topic: Data archiving. Archivers

By: Informatics

Completed by: 1st year student

A. V. Konshin

Checked by: Kolosova O.E.

Introduction

archiving packaging huffman

Nowadays, most of us often use the Internet and often come across information archived by various programs - archivers. This course work is devoted to the study of data archiving using the example of the WinRAR program.

The purpose of this course work is to disclose the concept of data archiving, studying the information compression algorithm, archiver programs and the process of packing and unpacking files using the WinRAR archiver program. Also, the aim of the course work is to consolidate knowledge and skills in working with Microsoft Word, Microsoft Excel, Microsoft Access.

Archivers are programs that allow you to reduce file size to save disk space. Their work is as follows: find duplicate fragments in files and write down information about the number of duplicate fragments instead. They can be divided into two classes: packers (archivers) and backup programs.

In the course of writing this course work, I use the knowledge acquired in computer science classes on the use of Microsoft Office XP programs: Microsoft Word, Microsoft Excel, Microsoft Access.

With Microsoft Word, I can create, edit, format, save and print documents. The Microsoft Word word processor has a wide range of document creation capabilities (inserting lists and tables, spell checkers, saving, correcting, etc.)

Microsoft Excel is a spreadsheet management program. A spreadsheet allows you to process large amounts of numerical data, such as experimental results, statistics, etc.

Microsoft Access is a database management system, part of Microsoft Office, that allows you to create databases, as well as provide processing (sorting) and data retrieval.

Data archiving (using the WinRaR program as an example)

Formulation of the problem. Write an abstract on a given topic on 12 - 15 printed sheets. In the abstract, provide for the use of bulleted and numbered lists, the insertion of a special character, the insertion of a footnote, a figure, the design of one of the paragraphs in the form of two columns.

Understanding File Archiving

One of the most widespread types of service programs are programs designed for archiving by compressing the information stored in them.

Compression of information is the process of converting information stored in a file into a form in which redundancy in its representation is reduced and, accordingly, less memory is required for storage.

Compression of information in files occurs by eliminating redundancy in various ways, for example, by simplifying codes, eliminating constant bits from them, or representing repeating symbols or a repeating sequence of symbols in the form of a repetition rate and corresponding symbols. Various algorithms for such information compression are used.

One or several files can be compressed, which in a compressed form are placed in a so-called archive file or archive.

An archive file is a specially organized file containing one or more files in compressed or uncompressed form and service information about the file names, the date and time of their creation or modification, sizes, etc.

The compression ratio of files is characterized by the coefficient Кс, defined as the ratio of the volume of the compressed file V c to the volume of the original file V о, expressed as a percentage:

Archiving (packing) - placing (loading) source files into an archive file in compressed or uncompressed form.

Unpacking (unpacking) - the process of restoring files from the archive exactly as it was before loading into the archive. When unpacking, the files are extracted from the archive and placed on disk or in RAM.

Archiving methods

There are two main archiving methods:

Huffman's algorithm. The algorithm is based on the fact that some characters from the standard 256-character set in free text can occur more often than the average repetition period, while others, respectively, less often. Therefore, if you use short sequences of bits less than 1 byte in length to write common characters, and longer ones to write rare characters, then the total file size will decrease. For example, the letters a, o, e, and - are very common in Russian text, the size of each letter is 1 byte (8 bits), they can be replaced with numbers 0,1,2,3, which can be placed in 2 bits. Those. the compression ratio will be 25%.

Lempel-Ziv algorithm. The classic Lempel-Ziv algorithm is LZ77, named after the year of its publication. It is formulated as follows: "if a similar sequence of bytes has already been encountered in an earlier text, then only a link to this sequence (offset, length) is written to the archive file, and not the text itself." So the phrase “BELL_BALL_BALL” is encoded in the sequence “KOLO (-4.3) _O (-6.4) _ (- 7.7) NI”. The compression ratio is 54%. The image is compressed in the same way. Large areas of the same color are replaced with a link: (color, length).

Archiving goals

Archiving is used as a means to reduce the size of a file - as a rule, it takes up less space in a file archive than in a normal state, and is mainly used for the following purposes:

· Free up space on your computer's hard drive.

· Reducing the volume of files sent by email.

· Placement of data on a single media.

· Placing 1 large file on multiple media when it does not fit on 1 media.

· Unpack compressed files.

Programs - archivers

The programs that pack and unpack files are called archiving programs.

Archive files that are large in size can be located on multiple disks (volumes). Such archives are called multivolume. A volume is an integral part of a multivolume archive. By creating an archive of several parts, you can write parts of it to multiple floppy disks.

Currently, several dozen programs are used - archivers, which differ in the list of functions and operation parameters. Among the most popular programs are:

WinZip, version 8.0 is perhaps the most famous archiver. It is the most popular archiver used on the Internet. It is often free or included in some other program as a free bonus. Beginning with the ME (Millenium Edition), WinZip is included even in Windows systems. In addition, there are many modifications of the WinZip archiver, such as zip - magic, 7 - zip, g - zip, etc., which differ in compression efficiency.

WinRar - the author of the program is Evgeny Roshal. The single-user system will cost you $ 29. You can download the test (trial) version from the website www.RaRlab.com. WinZip's main competitor on the Internet. Possessing the best characteristics, it gradually crowds out other formats, but so far it cannot cope with the authority of WinZip. A convenient (Russified) interface and a fairly high speed of work, combined with low system requirements, promise WinRar a good future.

WinAce 2.0 - a fresh version of the old archiver, enriched with very interesting functions and a new compression algorithm. This archiver uses the largest dictionary size for archiving (4 MB), which largely explains its high results.

There are highly specialized archivers that can work with only one file format, such as SfArk, which can only compress audio files in SF2 format. The WavPack archiver perfectly “compresses” sound files in the wav format. DJVU archiver specializes in compressing scanned images. There is also a whole galaxy of universal archivers such as UFA, 777, ACB, IMP, LZOP, UHARC, BOA, Arhangel.

There are many different archivers. The effectiveness of one or another archiver depends on several factors:

1. Contents of the compressed file (text, graphic, sound).

2. From which program is selected as the archiver.

3. From the settings of the program - archiver.

Types of archive files

In the computer file system, archive files have a strictly specified type (extension). So, the most common archives are of the type: ZIP, RAR, ARJ.

In addition to them, archives are used on computers: CAB, LZH, TAR, GZ, UUE, BZ2, ISO, etc.

Packing files

Let's consider working with the WinRaR archiver. There are three different ways to package a file.

· Using the WinRaR packaging wizard.

· Using the Windows context menu, if you have embedded WinRaR into the shell.

Directly in the WinRaR program itself, without the help of the wizard, by clicking on the button Add to or using the context menu of the WinRaR program itself.

Let's consider all three ways.

Package files using a wizard

Ш Click on the button Masterthe first dialog will appear on the screen Masters(fig. 1.1).

Figure 1.1 First Dialogue Master: Selecting actions

Ш To pack, click on the radio button Create new archive, then on the button Further.

Ш In the dialog that appears, click on the button of the drop-down list Folderand select the drive where the files you want to pack are located - click on the drive letter with the mouse (Fig. 1.2).

Figure: 1.2. Dialog Select the files to add

Ш Select in the working field of the dialog the folder or file that you will pack - select them. Click the button OK.

Figure 1.3. Dialog Choice names for future archive

Ш A dialog will appear on the screen Wizard: Select Archiveas shown in fig. 1.3. In the input field Archive name enter the name of the future archive.

Ш Click on the button Further... A dialog will appear on the screen Wizard: Archiving Optionsas shown in Fig. 1.4. In this window, you can make certain settings for archiving, check the boxes in the corresponding fields.

Figure: 1.4. Dialog Wizard: Archiving Options

Ш Click on the button Donethus starting the packaging process.

Figure: 1.5. Dialog Archive creation

After the words Archive creation the name of the future file is displayed in the dialog name (Fig. 1.5). The archive file will be located in the same location as the original folder.

Packing files from the Windows context menu

Let's zip the text file created earlier in Microsoft Word. If you chose EmbedWinRaR in a shell, you can do this:

Ш Go to the file on the disk using Windows Explorer.

SH Right click on the file.

Ш Click in the context menu on the line Add to archive

Ш In the appeared window (Fig. 1.6) click on the button OK.

Figure: 1.6. Dialog Name and parametersarchive

Packing files from the WinRaR program itself

Packaging from the WinRaR program itself provides more options than the previous two methods. In this method, you can implement the program settings in the most complete way. First, let's zip a text file created earlier in Microsoft Word.

Ш Open WinRaR.

Ш In the file window, select the file to be packed, then click the button Add. A dialog will appear on the screen Archive name and parameters with open tab General (Figure 1.6.)

Ш Click on the button OK... The archive file will be created in the same location as the original files.

Packaging directly from the WinRaR program in this case is almost no different from packaging from the Windows context menu.

Only in the latter case it was necessary to start the WinRaR program first, and in the first case it started automatically.

Archiving profiles

You can do all the settings yourself or use the ready-made settings made by the author of the program by clicking on the button Profiles,as shown in Fig. 1.6. There are only 5 profiles here, the most suitable, according to the author of the programs, for solving the most urgent tasks when archiving:

· Default profile - nothing will change, until the pack you want to change the default profile itself.

· Attaching toe - mail - the most optimal for creating an archive, which will then be sent by e-mail.

· Backup of selected files - optimal for creating an archive with files important to you.

· Volumes of 1.44 MB - the archived file will, if necessary, be automatically split into several files (they are called volumes) with a size of 1.44 MB - so that each of them will fit on a standard floppy disk.

· Zip - archive (low compression ratio) - select it if you want to create an archive in the format zip.

If you are not completely satisfied with the existing profiles, you can create your own in any number. First, you need to make the desired settings on the corresponding tabs of the dialog Archive name and parametersas shown in Fig. 1.6.

Ш After that open the tab General, then click the button Profiles and in the resulting context menu - on the line Save the current setting as a new profile. A dialogue appears on the screen Profile parametersas shown in Fig. 1.7.

Figure: 1.7 Dialogue Profile parameters

Ш In the input field Profile name type in the desired name - after saving it will be displayed in the list when you click on the button Profiles.

Ш Save profile.

Archive format, compression method and volumes

Settings on the tab General... In a group of controls Archive formatchoose in which format you want to create the archive - zip or RaR.

Ш Click on the required radio button.

Ш In the drop-down list of the same name, select Compression method... Remember that speed and compression are closely related to each other. The higher the speed, the lower the compression ratio and vice versa.

If you need to split the archive into several parts, use the drop-down list Divide into volumes in size (in bytes).The created archive will be divided into several files of the same size - pieces, each of which will be assigned a serial number.

Archiving options

Let's move on to the next group of controls (Figure 1.6) - Archiving options.

· Delete files after packing... If the checkbox is checked, the original files will be deleted immediately after packing - only the created archive will remain.

· When you select the Create SFX - archive checkbox, a self-extracting archive will be created (SFX is an abbreviation of the words Self Extractor), a wonderful feature provided by the archiver.

Figure: 1.8. Dialog Self-extracting archive

The next control is Create continuous archive... Check the box if you want to increase the compression ratio even more.

· Add electronic signature - an electronic signature will be added to the archive, containing the name of the author who created the archive, the date of the last update and the original name. This setting is only available in a registered program.

· Add information for recovery — when the checkbox is checked, the information for recovery will be written to the archive, which will be used in case of archive damage. The size of the archive will increase slightly (by default, by 1% of the original text).

To do this, follow these steps.

Check the box Dadd recovery information.

Go to the tab Dadditionallyby clicking on its shortcut with the mouse, and in the field Recovery information enter in the input field with the counter% of the total archive size.

· Test the file after packaging - if you check the box, then after packing the archive will be checked for errors. If you also check the box at the same time Delete file after packing, then the original files will be deleted only if the newly created archive does not contain errors.

· Lock archive. When the checkbox is checked, it will be impossible to change the created archive - it will no longer be possible to add files to it or delete files from it, etc. Although you can unpack the archive just like any other.

Creating a multivolume self-extracting archive

The new file is saved in the folder My documents.

Find the file and right click on it. In the menu that opens, click on the line add to archive. A dialog will appear Archive name and parameters.

After that, you need to make the necessary settings for the archiver.

Ш On the tab General click on the dropdown button Divide into volumes in size (in bytes) and select item Auto detect.

You will need to select the location where the file will be archived. In this case, it is a floppy disk.

Open the floppy disk - click the browse button to open a dialog Archive search... Click on the drop-down list Folder, then when the list opens, on the line Disk 3.5 A and then on the button Open.

As a result, the path to the floppy disk will be indicated in the Archive name input field.

W Click OK. A dialog will appear on the screen Archive creation.

All files and folders on the floppy disk will be deleted. Instead, one of the archive volumes will be written. After the free space on the first floppy disk runs out, a dialog will appear on the screen Next volume... Remove the floppy disk from the floppy drive, insert a new one and click on the button Create a... Continue this way until the last archive file is created.

A multi-volume self-extracting archive was created and written to floppy disks.

Unpacking files

Just like packing, files can be unpacked in at least three ways:

· Using the WinRaR wizard.

· From the Windows context menu.

· From the WinRaR program itself, without using the wizard.

Unpacking files using WinRaR wizard

Ш Open WinRaR.

Ш Start the wizard. In dialogue Wizard: Selecting Actionsas shown in Fig. 1.1, click the switch Unpack the archive.

Ш A new wizard dialog will appear on the screen, which in this case will be called Wizard: Select Archive (Fig. 1.9).

Fig 1.9. Dialog Master: Archive selection

Ш Select the archive you want to unpack.

Select the archive file and then click on the button Open.

Dialogue reappears on the screen Wizards: Archive Selection... But the path to the file will now be displayed in the Archive name input field.

W Click Further.

A new dialogue will appear Wizard: Select folder for unpacked files.

Figure: 1.10. Dialog Selecting a folder for unpacked files

W Click Done.

The archive will be unpacked, and a window will automatically open with the folder into which the archive is unpacked.

Unpacking an archive using the Windows context menu

Unpacking from the context menu is convenient because you do not need to find WinRaR in the start menu or on the Windows desktop every time - the context menu is always at hand. Finding the file you want to unzip is quite easy by the icon in the form of a stack of books tied with a belt.

Find the file you want to unpack.

Ш Right-click the archive file. Several lines related to unpacking will appear on the screen in the context menu:

· Extract files …

· Extract to current folder

Extract to Folder Name

Ш In the displayed context menu, click on the line Extract files.A dialog will appear on the screen Extraction path and parameters, as shown in Fig. 1.11.

Ш Click on the button OK... The archive will be unpacked.

Figure: 1.11. Dialog Extraction path and parameters

Unpacking the archive directly from the WinRaR program

This method is no more difficult than the previous ones. At the same time, you have much more opportunities than with other methods. For example, you can extract only part of the files from the archive, or delete some files from the archive, you can even read the contents of the files if it is a simple text document.

Ш Start the WinRaR program.

Ш Open the disk where the archive is located.

The file window will display the contents of the root directory of the disk - i.e. all files and folders located in the root directory.

Find and highlight the archive file.

Ш Click the button Extract... A dialog will appear on the screen Extraction path and parameters (Fig. 1.11.)

Ш Click the OK button. The archive will be unpacked to a folder on the disk.

Unpacking a self-extracting archive

Let's unpack a self-extracting archive written on several floppy disks.

Ш Insert the floppy disk containing the first self-extracting archive file.

Ш Open Windows Explorer, open the floppy disk in Explorer and make double cheeks on the file with the left mouse button. A dialog will appear on the screen Self-extracting archiveWinRaR.

Ш Using the button Overview select the drive or folder to unpack.

Ш To start unpacking, click on the button Extract... After a while, the program will ask for the next floppy disk in the dialog next volume is required.

Ш Insert the floppy disk and click the OK button.

Ш Repeat these steps until the dialogue Requiresxia next volume does not disappear from the screen.

You can do it differently. Open the first floppy disk in Explorer and copy the first archive file to a folder. Then everything, as in the previous case, only much faster.

Conclusion

In the course of this course work, I studied several information compression algorithms, revealed the concept of data archiving using the example of the WinRaR program. Now I know that an archiver is a program that creates archives - a special file in which a variety of files and folders can be compressed. Ultimately, it all boils down to two operations - packing into an archive and unpacking from it.

After completing the coursework, I can pack individual files and entire folders, extract files from archives, change, supplement archives. I can create a self-extracting archive that does not require any additional program to unpack.

Also, in the process of doing the work, I consolidated my knowledge and skills of working with Microsoft Word, Microsoft Excel, Microsoft Access.

Literature

1. E. Lemon, 2 and 1: Modern computer. Key topics + Video course: [tutorial] / ed. E. Lemon. - M .: Triumph, 2007.-320s.

2. Makarova N.V., Informatics: Textbook / Ed. Prof. N.V. Makarova. - M .: Finance and statistics, 1997.-768 p .: ill.

3. Simonovich S.V. Informatics. Basic course / S.V. Simonovich. - SPb .: Peter, 2006 .-- 688 p .: ill.

4. Computer science. Microsoft Access XP: Methodological instructions for laboratory work for students of specialties 060803, 260100, 260200 I course of full-time education. - Krasnoyarsk: SibSTU, 2005 .-- 30 p.

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