EPSON | Presenters Online : Basics > Visuals > The Basics of File Compression

File compression is a means of reducing file size by encoding the file contents. Because compressed files are smaller and easier to maneuver, file compression is commonly used when storing files or when transferring files from one location to another. The smaller a file is, the less storage space it requires and the less time it takes to transfer to different locations.

File compression is a type of computer shorthand. When you compress a file, the compression software looks for a series of repeating characters or bits in the file. The software then replaces these blocks of repeated characters with symbols or shorter words or phrases that are called "tokens." When you apply a decompression program to a compressed file, the software reads the file and replaces the tokens with the original data, inflating the file back to its original size.

It is especially important to understand file compression when dealing with multimedia presentations. Often, presentation files are HUGE and compressing them is the only way to transfer them from one location to another without going across a network.

Types of File Compression

There are countless programs you can use for file compression. The most popular compression programs and their associated file extensions are as follows:

Platform

Compression Program

File Extension

Mac

Stuffit

.sit

PC

WinZip

.zip

UNIX

Compress

.Z

The most important thing to remember about compressing files is that you must use the same program to compress and uncompress (extract) any given file.

Note
There is one caveat to this statement. Many zip programs, such as WinZip, create self-extracting files. So, the individual who opens the zip file simply clicks on the file.zip and the file is extracted. The user does not need the "unzip" application.

PC Platform

"Zipped" files (*.zip) are one of the most common types of compressed files. There are a number of Windows-based program utilities that compress and expand zipped files. Two of the most common are PKZIP, a product of PKWARE Inc., and Winzip, which is published by WinZip Computing Inc.

Where to Get a File Compression Application

So, now you know a bit about file compression and are ready to try to zip a file. Many popular compression programs provide free trial versions on the web. For example, if you are using a PC, you can use WinZip. Just go to www.winzip.com and look for free "evaluation copies" that you can download and use right away. Please note that WinZip is "shareware" which means you are free to use it for a certain amount of time. If you continue to use the program after this time period, you should send a check in to the specified address to compensate the developer.