Web User guide to file compression

Tue, 6 Feb 2007
Andy Shaw
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There are lots of different types of compressed file formats available and, in issue 155 of Web User, we conducted a group test of the programs you can use to compress and decompress them. But what's the difference between an ARJ and a ZIP? Refer to our table below to find out.

Format	File extension	Description
7z	.7z	Excellent compression level, requires (free) 7-Zip software
ARC	.arc	Programs supporting this may open older archives but it's now rarely used to compress files in its own right
ARJ	.arj	As above, programs supporting this may open older archives but it's now rarely used to compress files in its own right
BZIP2	.bz2	Good compression ratio but it's slower than ZIP and GZIP formats
GZIP	.gz	The version of ZIP often used on Linux computers
LHA	.lha	The compression file format used on the Commodore Amiga, which was a popular home computer back in the 1980s
RAR	.rar	Excellent compression level but only available with WinRAR software. However, decompression can be achieved with other software
SIT	.sit	The most popular compression format on Apple's computers though its compression ratio has been surpassed by modern standards
TAR	.tar	An older file format, used in conjunction with other compression, that isn't seen very much any more
ZIP	.zip	The file format most commonly used on Windows PCs that offers a decent balance between size, speed, ease of use and compatibility