As Seen on TV!
Have you ever seen that late-night television ad for the Travel Genie, a device that claims to squeeze clothing together so tightly that you can fit two or three times more than normal into a suitcase? Well, the same idea is at work with file compression!
What Is File Compression?
File compression allows you to squeeze your data, greatly reducing the file size. Why would you want to do this? By reducing file size you can send and receive files over the Internet more quickly, store more files on your hard drive, and pack many related files into one archive (for example, all files related to the same project).
How Does File Compression Work?
File compression works by eliminating repetitive "bits and bytes" — the basic units of computer storage. For example, let's say each letter, space, and punctuation mark occupies one unit of space on your hard drive. The phrase "A horse! A horse! My kingdom for a horse!" would take up 41 units of space (30 letters, 8 spaces, and 3 exclamation points). But what if we replaced the repeated word "horse" with a single character, such as the number "1"? The phrase would then read "A 1! A 1! My kingdom for a 1!," which takes up only 29 characters, saving 12 characters and 28 percent of the file size. After sending the file, all we would need to do is replace each "1" with the word "horse" to reconstruct the original sentence. (We would also need to include the coding scheme, which adds to the file size, so that the receiver would know to make the replacement. That's why compressing a small file sometimes saves no space and may even enlarge the file.)
File Compression Programs
Many popular file compression programs are available for download on the Internet. For Windows computers, WinZip, utilizing the zip file format, is extremely popular. It is available for a free 21-day evaluation at www.winzip.com. Another popular Windows compression product is PKZip.
StuffIt is extensively used on Macintosh computers; Windows and Linux versions are also available. In addition to its own file format, StuffIt also supports the zip format (amongst others). If you only need to decompress files you receive, Unstuffit is a free program that you can download from the StuffIt Web site.
Macintosh OS X has built in file compression available; just click a file icon or name and choose "Archive" from the File menu to create a zip-compressed version of the file.
How Do I Use a File Compression Program?
It's easy to use most file compression programs; with many products, you can simply drag a file and drop it on the program's desktop icon to create a compressed version. In addition, if you have compression software installed, right-clicking (or control-clicking on a Mac) on a file icon frequently brings up a menu that allows you to choose to compress the file.
Jeffrey Branzburg is a contributing editor and regular columnist for Technology & Learning.
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