Your Internet Consultant - The FAQs of Life Online

6.15. What's with all these filename extensions, file formats, and archiving systems?

How a file has been translated and compressed is usually indicated by the filename's suffix. Normally a file will have a name something like filename.sit.hqx. In this example, sit indicates how it was compressed and hqx indicates how it was translated. Before you can use any programs or view any graphics tweaked with any compression or translation tools, you'll need to turn the file back into its pristine original; for instance, by unBinHexing and then unStuffing the file. (By the way, BinHex is used exclusively on Macintosh files.)

Some anonymous FTP sites make a habit of modifying files twice, first compressing them and then changing binary files to text format (so that they can easily pass through mail gateways and other computer systems that don't handle binary files).

There is a wonderful document that lists zillions of file compression, translation, and archiving formats along with their filename extensions and information on where to find the software to uncompress, translate, and "unarchive" files in these formats. It lists file formats that I never knew (and would rather not know) existed: ones with names like BLU, Disk-Masher, Ish, terse, Whap, and yabba. (May the gods of Internet smile on you and keep those arcane files far away from you.) Anyway, get this document, available by FTP: 

ftp.cso.uiuc.edu directory:/doc/pcnet/compression.
There is a FAQ posting that deals exclusively with picture file formats. It is posted regularly to alt.binaries.pictures.fine-art.d It is available via anonymous FTP.

For e-mail access, send a message 
To: mail-server@rtfm.mit.edu
Subject: <subject line is ignored>
Body: send usenet/news.answers/pictures-faq/*
Here's a list of some of the most popular archive systems, translation methods, and file formats. Rest assured that there are hundreds more. 
Archive	Compression Standards

Table of Contents | Previous Section | Next Section