File Compression

While surfing the Internet, you will undoubtedly find audio and video files to download. Since media files, especially full length movies can be very large, downloading them may take hours, depending on the speed of your Internet connection.

To speed things up and make efficient use of disk space, many large files are compressed. File compression reduces the size of a file, shortening the time it takes to download. Compression software uses complex mathematical equations to scan a file for repeating patterns in the data. It replaces the data with smaller codes that take up less room. For example, one way compression software works is to replace repeating text characters with a code that also notes the locations of those characters in the data. With a picture, it would find all of the red pieces, for example, and replace them with a code.

To view compressed files, you need a compatible decompression program that reads these codes and converts the data to its original form.

Most of the files you encounter on the Web are either text, graphics, audio, or video files. Some may be compressed, others not. The most common compressed files are those with extensions such as .zip, .sit and .tar. These extensions represent popular compression formats for the PC, Macintosh, and Linux. They may be a single file or groups of files that have been bundled into a single archive. An archive file can sometimes contain any type of file and often contains software programs with related documentation.

To decompress a .zip file you need an utility like WinZIP. To unstuff a file with a .sit extension, you need a program called Stuffit Expander, a popular program for the Mac. Though WinZip will not decompress files that have been "stuffed," there is a StuffIt Expander version for Windows. StuffIt Expander can also decompress other formats, including .zip

Files with a .sea or .exe extension are self-extracting files for the Macintosh and Windows. They don't require additional software to run. You simply click on the file to launch it.

For more information about compression, read the Compression FAQ. To download decompression software, visit Shareware.com.

Last update: Jan 12, 2010