Presentation on computer science "Archivators. Data archiving"

Compression methods. Lossy compression With lossy compression, some information is lost, but this remains invisible to humans. For example: – When compressing video recordings of fast-moving objects, small details can be neglected; –When compressing sound with quiet sounds against the background of loud ones; –When compressing graphics, replace the color of neighboring pixels with a similar value.

Huffman Algorithm The Huffman method takes into account the probability of objects appearing and encodes them with codes of varying lengths. For example, in the Russian alphabet the letters O, E, A are common, F, Ts, Shch, E are rare. The more often a letter appears, the shorter the code used for it. This coding principle is used in Morse code: E A – E –

Lempel-Ziv-Welch algorithm The LZW (Lempel, Ziv, Welch) algorithm was invented in 1977 by mathematicians Abraham Lempel and Jacob Ziv, and in 1984 it was modified by Terry Welch. This method is a “sliding window” method. The algorithm encodes strings of characters (patterns), placing them in a table and replacing them with a shorter code. If such a chain is encountered again, then not the chain itself, but its shorter code will be placed in the output file.

RLE algorithm RLE (Run Length Encoding) run length encoding: a series of repeating bytes is replaced by one repeating byte and a repetition counter ABVGDEJZI?

WinRAR features Full support for archives in RAR and ZIP formats; Original highly efficient data compression algorithm; Unpacking files in CAB, ARJ, LZH, TAR, GZ, ACE, UUE, BZ2, JAR, ISO, 7Z, Z formats; Creation of self-extracting, continuous and multi-volume archives; Adding additional information to archives to restore the archive in case of damage; Ability to protect the archive with a password.

Self-extracting archive Self-extracting archive (SFX self-extracting archive) is a file with a *.exe extension that combines an archive and executable code for unpacking it. Such archives, unlike regular ones, do not require a separate program to extract files from the archive, but are larger in size. Using self-extracting archives is convenient when it is not known whether the user to whom the archive is being transferred has the appropriate unpacking program.

Continuous archive Continuous archive is an archive packaged in such a way that all compressed files are treated as one continuous data stream. The advantages of continuous archive include a significant increase in the compression ratio. Moreover, the smaller the average file size, the larger the files themselves and the more similar files to each other, the greater the compression ratio. The disadvantage of a continuous archive is that adding or deleting files is slower than when working with regular archives.

Multivolume archive Multivolume archive is an archive divided into several parts (volumes). The need to split an archive into volumes arises, for example, when using floppy disks, if after compression the size of the archive exceeds the size of one floppy disk. The ability to work with multi-volume archives can be useful when working with email, when the email program allows you to attach only one file for sending or the mail server allows you to attach a file of limited size to a letter.

Extracting files from an archive using the context menu Extract files... allows you to specify the path for extraction. Extract to current folder will extract files from the archive to the current folder. Extract to will create a folder with the name of the archive and place the extracted files there.

Creating an archive using the context menu Add to archive... allows you to add files to the archive by specifying the location, name, archive format, compression method and archiving parameters. Add to archive.rar will create an archive with the same name as the file or folder and default settings.

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Slide captions:

Data archiving

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 a reduction in the physical size of files in which data is stored, without significant information loss.

The best archived files are Text files (in TXT, RTF, DOC format, etc.) Excel tables Various databases EXE program files They can be compressed several times, but they are completely and error-free “unpacked” at any necessary time.

Graphic files in .BMP format are best archived. But it is almost impossible to compress .JPG or .GIF picture files, .MP3 and .WMA music files, .AVI and .WMV video files using an archiver, perhaps just a little. In addition, there is no point in archiving the archive itself - there will be no compression.

Archivers are programs (a set of programs) that perform compression and restoration of compressed files in their original form. The process of compressing files is called archiving. The process of recovering compressed files is by unzipping.

Archiver WinRAR Features of WinRAR: Allows you to unpack archives CAB, ARJ, JAR, etc. Provides archiving of data in ZIP and RAR formats Provides full support for ZIP and RAR archives Supports drag & drop technology Provides recovery of physically damaged archives

WinRAR features: Provides the ability to create multi-volume archives, that is, it splits the archive into several parts (volumes) (for example, to write a large archive to disks). Volume expansion: RAR, R01, R02, etc. With a self-extracting archive, the first volume has an EXE extension Creates self-extracting archives (SFX) regular and multi-volume archives, provides password protection Has recovery tools that allow you to restore missing parts of a multi-volume archive WinRAR is able to create an archive in two different formats: RAR and ZIP.

FORMAT.ZIP 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 send the email attachment in ZIP format. You can also send a self-extracting archive. Such an archive is a little large, but can be extracted without external programs. Another advantage of ZIP is speed. A ZIP archive is usually faster to create than a RAR archive.

The RAR format provides significantly better compression than ZIP. FORMAT.RAR Appearance of the WinRAR archiver

Thank you for your attention! The presentation was prepared by Yu.V. Belousova, Computer Science Teacher of the State Autonomous Educational Institution of Secondary Professional Education KO “College of Service and Tourism”.

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Compression methods. Lossy compression With lossy compression, some information is lost, but this remains invisible to humans. For example: – When compressing video recordings of fast-moving objects, small details can be neglected; –When compressing sound with quiet sounds against the background of loud ones; –When compressing graphics, replace the color of neighboring pixels with a similar value.

Huffman Algorithm The Huffman method takes into account the probability of objects appearing and encodes them with codes of varying lengths. For example, in the Russian alphabet the letters O, E, A are common, F, Ts, Shch, E are rare. The more often a letter appears, the shorter the code used for it. This coding principle is used in Morse code: E A – E –

Lempel-Ziv-Welch algorithm The LZW (Lempel, Ziv, Welch) algorithm was invented in 1977 by mathematicians Abraham Lempel and Jacob Ziv, and in 1984 it was modified by Terry Welch. This method is a “sliding window” method. The algorithm encodes strings of characters (patterns), placing them in a table and replacing them with a shorter code. If such a chain is encountered again, then not the chain itself, but its shorter code will be placed in the output file.

RLE algorithm RLE (Run Length Encoding) run length encoding: a series of repeating bytes is replaced by one repeating byte and a repetition counter ABVGDEJZI?

WinRAR features Full support for archives in RAR and ZIP formats; Original highly efficient data compression algorithm; Unpacking files in CAB, ARJ, LZH, TAR, GZ, ACE, UUE, BZ2, JAR, ISO, 7Z, Z formats; Creation of self-extracting, continuous and multi-volume archives; Adding additional information to archives to restore the archive in case of damage; Ability to protect the archive with a password.

Self-extracting archive Self-extracting archive (SFX self-extracting archive) is a file with a *.exe extension that combines an archive and executable code for unpacking it. Such archives, unlike regular ones, do not require a separate program to extract files from the archive, but are larger in size. Using self-extracting archives is convenient when it is not known whether the user to whom the archive is being transferred has the appropriate unpacking program.

Continuous archive Continuous archive is an archive packaged in such a way that all compressed files are treated as one continuous data stream. The advantages of continuous archive include a significant increase in the compression ratio. Moreover, the smaller the average file size, the larger the files themselves and the more similar files to each other, the greater the compression ratio. The disadvantage of a continuous archive is that adding or deleting files is slower than when working with regular archives.

Multivolume archive Multivolume archive is an archive divided into several parts (volumes). The need to split an archive into volumes arises, for example, when using floppy disks, if after compression the size of the archive exceeds the size of one floppy disk. The ability to work with multi-volume archives can be useful when working with email, when the email program allows you to attach only one file for sending or the mail server allows you to attach a file of limited size to a letter.

Extracting files from an archive using the context menu Extract files... allows you to specify the path for extraction. Extract to current folder will extract files from the archive to the current folder. Extract to will create a folder with the name of the archive and place the extracted files there.