FILE COMPRESSION FORMATS

---

File compression formats typically pack one or more files into a single file that’s smaller than the sum of all the parts. The most popular file compression formats work on several operating systems but some file compression formats are only used on specific operating systems, such Linux or Mac OS X, which limits their file sharing opportunities.

Note

Note Although file compression formats can squash multiple files into a single file, they don’t always work on certain types of files that are already compressed, such as certain movie, photo, and music file formats. Trying to compress MP3 or JPEG files with a file compression program can actually increase the total size of the file.

Here’s a look at the most common compression formats traded on the Internet, the type of information they usually contain, and the programs used to create or open them.

ZIP

Type of file: Lossless compression

Usual contents: Any type of file

Copy protection: Optional password protection

Official website: None

Programs used: PKZIP (http://www.pkzip.com) and WinZip (http://www.winzip.com) for Windows; ZipIt (http://www.maczipit.com) and StuffIt (http://www.stuffit.com ) for Macintosh

Zip is one of the oldest lossless compression formats around, and it combines-several files by compressing them all into a single file. Retrieving all of the files is as simple as “unzipping” the single zipped file.

Although other formats are more efficient at compressing files, Zip works on nearly every type of computer, making it useful for compressing files that nearly anybody can download and unzip. For optional protection, you can password-protect a Zip file.

RAR

Type of file: Lossless compression

Usual contents: Large files like movies or entire albums

Copy protection: Optional password protection

Official website: http://www.rarlabs.com

Programs used: WinRAR for Windows and RAR for most other operating systems (http://www.rarlabs.com)

The RAR compression standard can compress files up to 15 percent smaller than Zip. Available for Windows, Macintosh, Linux, Pocket PC, FreeBSD, Unix, and many other operating systems, the RAR and WinRAR (for Windows) programs can not only compress and uncompress RAR files, but Zip files and several other file compression formats as well.

PAR AND PAR2

Type of file: Recovery

Usual contents: Recreates missing RAR files

Copy protection: No

Official website: http://parchive.sourceforge.net

Programs used: QuickPar (http://www.quickpar.org.uk)

Few things are more frustrating than downloading 105 RAR segments of a movie only to find that four of the pieces are missing or corrupt, leaving gaps. If you can’t find those pieces anywhere, there’s still a chance you can recreate them using PAR files.

PAR’s popularity is being overtaken by a newer, better way of reconstructingmissing PAR files, called PAR2. The PAR2 specification supports both PAR and the newer, more efficient PAR2 files.

YENC

Type of file: Lossless compression

Usual contents: Music or video files, usually posted on newsgroups

Copy protection: No

Official website: http://www.yenc.org

Programs used: Almost all dedicated newsreader programs

Because newsgroups only accept text, people can only trade songs and movies over newsgroups by first converting (encoding) these files into text, which can then be converted (decoded) back into the original format. One of the more popular file compression programs for trading files over newsgroups is the yEnc public domain encoding method.

---