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ITEC 325 Spring 2013 Assignment 3 Working individually describe the compression/archive utilities listed below: • 7-zip • gzip • rar • tar • zip For each utility, do the following: • Write a description of how the utility operates • List the most common arguments & describe the effect of that argument • Briefly describe any compression algorithms implemented by the utilities Create a summary table that compares and contrasts the different utilities. Cite any references you will use to create the paper. Not citing sources will result in plagiarism. Also copying and pasting directly from the sources without properly citing will result in plagiarism. The result of plagiarism is a grade of 0 for the assignment and may lead to consequences described in the syllabus. You should use APA-style citation and reference formatting for this paper. You can find references on how to use the APA style at the following address: http://cooklibrary.towson.edu/styleGuides.cfm#APA
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• 7-zip
7-Zip is an open-source file archiver, an application used primarily to compress files. 7-Zip uses
its own 7z archive format, but can read and write several other archive formats. By default, 7-Zip
creates 7z-format archives with a .7z file extension. Each archive can contain multiple directories
and files. As a container format, security or size reduction are achieved using a stacked
combination of filters.
List of the most commons arguments:
7z:

name of executable

x:

use the extract command

a:

add to archive command

-r:

recourse all child directories

t:

test the specified archive

e:

use extract with full path command

u:

update command

d:

delete files

Compression algorithms
The following compression algorithms are currently defined:
LZMA – A variation of the LZ77 algorithm, using a sliding dictionary up to 4 GB in length for
duplicate string elimination. The LZ stage is followed by entropy coding using a Markov chainbased range coder and binary trees.

LZMA2 – modified version of LZMA providing better multithreading support and less
expansion of incompressible data.
Bzip2 – The standard Burrows–Wheeler transform algorithm. Bzip2 uses two reversible
transformations; BWT, then Move to front with Huffman coding for symbol reduction (the actual
compression element).
PPMd – Dmitry Shkarin's 2002 PPMdH (PPMII/cPPMII) with small changes: PPMII is an
improved version of the 1984 PPM compression algorithm (prediction by partial matching).
DEFLATE – Standard algorithm based on 32 kB LZ77 and Huffman coding. Deflate is found in
several file formats including ZIP, gzip, PNG and PDF. 7-Zip contains a from-scratch
DEFLATE encoder that frequently beats the de facto standard zlib version in compression size,
but at the expense of CPU usage.

• Gzip
Gzip is a file format and a software application used for file compression and decompression. is
based on the DEFLATE algorithm, which is a combination of LZ77 and Huffman coding.
DEFLATE was intended as a replacement for LZW and other patent-encumbered data
compression algorithms which, at the time, limited the usability of compress and other popular
archivers.
List of the most commons arguments:
✓ -c, --stdout

write on standard output, keep original files unchanged

✓ -d, --decompress

decompress

✓ -f, --force

force overwrite of output file and compress links

✓ -h, --help

give this help

✓ -k, --keep

keep (don't delete) input files

✓ -l, --list

list compressed file contents

✓ -L, --license

display software license

✓ -n, --no-name

do not save or restore the original name and time stamp

✓ -N, --name

save or restore the original name and time stamp

✓ -q, --quiet

suppress all warnings

✓ -r, --recursive

operate recursively on directories

--rsyncable

make rsync-friendly archive

✓ -S, --suffix=SUF

use suffix SUF on compressed files

✓ -t, --test

test compressed file integrity

✓ -v, --verbose

verbose mode

✓ -V, --version

display version number

✓ -1, --fast

compress faster

✓ -9, --best

compress better

Compression algorithms
The deflation algorithm used by gzip (also zip and zlib) is a variation of LZ77. It finds duplicated
strings in the input data. The second occurrence of a string is replaced by a pointer to the
previous string, in the form of a pair (distance, length). Distances are limited to 32K bytes, and
lengths are limited to 258 bytes.

• Rar
RAR is a proprietary archive file format that supports data compression, error recovery and file
spanning. are based on lossless compression. RAR remove the redundant information when you
compress (or “zip”) the file and restore it when you uncompress (or “unzip”)...

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