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Desktop Software



    

Compression Utilities    

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Compression Utilities



Oct
03

 

file compression programs

File compression is a computer software technology/algorithm and/or a piece of software that you could use to save disk space by converting the file from one format to another fixed extension  file format that can only be opened by its propriety software allowing the users to save disk space by keeping the final file received after the compression process done by the utility in the form of a lossless compression.

There are several file compression utilities available henceforth for the various compression algorithm's which are as follows:

winzip download

.zip

Windows has inbuilt utility for converting the files to zip file format. you can use this utility by selecting the file AND/OR folder to be compressed and then do a right-click and then select Send To → Compressed ( zipped ) folder.

There is also a freeware app available for this purpose as well called WinZip.

We are not giving the download links for winrar because it is already built-in onto windows and this type of compressed files (.zip files) can be handled by winrar (together with other formats)

 

winrar

.rar

RAR stands for Roshal ARchive. It is a proprietary archive file format that supports data compression, error recovery, and file spanning. It was developed by a Russian software engineer, Eugene Roshal (the first letter of his surname contributing to the name of the archive format), and is currently licensed by win.rar GmbH.

Reference: http://en.wikipedia.org/wiki/RAR

The freeware program for uncompressing and compressing files/folders to .rar extensions are as follows:

WinRAR

Official Website :http://www.rarlab.com/

Get the download links here:

 

gzip

.gz

gz stands for gunzip and it is the most and the best compression technique available on the planet. While gunzip is the most popular on the internet and in the Linux world .zip does the same over windows

You can use WinRAR for the purpose of uncompressing and compressing archives to .gz file format

Gzip reduces the size of the named files using Lempel-Ziv coding (LZ77). Whenever possible, each file is replaced by one with the extension .gz, while keeping the same ownership modes, access and modification times. (The default extension is -gz for VMS, z for MSDOS, OS/2 FAT, Windows NT FAT and Atari.) If no files are specified, or if a file name is "-", the standard input is compressed to the standard output. Gzip will only attempt to compress regular files. In particular, it will ignore symbolic links.

If the compressed file name is too long for its file system, gzip truncates it. Gzip attempts to truncate only the parts of the file name longer than 3 characters. (A part is delimited by dots.) If the name consists of small parts only, the longest parts are truncated. For example, if file names are limited to 14 characters, gzip.msdos.exe is compressed to gzi.msd.exe.gz. Names are not truncated on systems which do not have a limit on file name length.

By default, gzip keeps the original file name and timestamp in the compressed file. These are used when decompressing the file with the -N option. This is useful when the compressed file name was truncated or when the time stamp was not preserved after a file transfer.

Compressed files can be restored to their original form using gzip -d or gunzip or zcat. If the original name saved in the compressed file is not suitable for its file system, a new name is constructed from the original one to make it legal.

gunzip takes a list of files on its command line and replaces each file whose name ends with .gz, -gz, .z, -z, _z or .Z and which begins with the correct magic number with an uncompressed file without the original extension. gunzip also recognizes the special extensions .tgz and .taz as shorthands for .tar.gz and .tar.Z respectively. When compressing,gzip uses the .tgz extension if necessary instead of truncating a file with a .tar extension.

gunzip can currently decompress files created by gzip, zip, compress, compress -H or pack. The detection of the input format is automatic. When using the first two formats, gunzip checks a 32 bit CRC. For pack, gunzip checks the uncompressed length. The standard compress format was not designed to allow consistency checks. However gunzip is sometimes able to detect a bad .Z file. If you get an error when uncompressing a .Z file, do not assume that the .Z file is correct simply because the standard uncompress does not complain. This generally means that the standard uncompress does not check its input, and happily generates garbage output. The SCO compress -H format (lzh compression method) does not include a CRC but also allows some consistency checks.

Files created by zip can be uncompressed by gzip only if they have a single member compressed with the 'deflation' method. This feature is only intended to help conversion of tar.zip files to the tar.gz format. To extract zip files with several members, use unzip instead ofgunzip.

zcat is identical to gunzip -c. (On some systems, zcat may be installed as gzcat to preserve the original link to compress.) zcat uncompresses either a list of files on the command line or its standard input and writes the uncompressed data on standard output. zcat will uncompress files that have the correct magic number whether they have a .gz suffix or not.

Gzip uses the Lempel-Ziv algorithm used in zip and PKZIP. The amount of compression obtained depends on the size of the input and the distribution of common substrings. Typically, text such as source code or English is reduced by 60-70%. Compression is generally much better than that achieved by LZW (as used in compress), Huffman coding (as used inpack), or adaptive Huffman coding (compact).

Compression is always performed, even if the compressed file is slightly larger than the original. The worst case expansion is a few bytes for the gzip file header, plus 5 bytes every 32K block, or an expansion ratio of 0.015% for large files. Note that the actual number of used disk blocks almost never increases. gzip preserves the mode, ownership and timestamps of files when compressing or decompressing.

.xz

.xz is another file format which you might find being used here and there.

More info can be found here: http://tukaani.org/xz/format.html 

The .xz file format is a container format for compressed streams. There are no archiving capabilities, that is, the .xz format can hold only a single file just like the .gz and .bz2 file formats used by gzip and bzip2, respectively.

Compared to a few other popular stream compression formats, the .xz format provides a couple of advanced features. At the same time, it has been kept simple enough to be usable in many embedded systems.

The utility is as herewith:

Download xz version 5.0.3 for windows :: all versions here

 

The compression algorithms are given in detail in the developer section of this website. Here are those links:

.zip .rar .gz .xz



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