Working with Zip Files

The larger a file is, the longer it takes to download. So some files online are compressed—converted into smaller files—to cut the download time. After downloading, you must decompress a compressed file to restore it to its original size and use it.

Also, most application programs are made up not just of one fat file, but of a collection of program and data files. A single compressed file can pack together many separate files, so they can all be downloaded together in one step. When you decompress a compressed file containing multiple files—which is sometimes called an archive—the files are separated.

Several forms of compression are used online, but most compression programs create archive files that use a format called Zip. A Zip file uses the extension .zip, and it must be decompressed—unzipped—after downloading before you can use the file or files it contains.

You need a special program to unzip Zip files. If you don't already have one, the most popular shareware unzippers

• For Windows are WinZip, which you can download from www.winzip.com, or PKZip, which you can get from PKWare at www.pkware.com.

• For Macintosh is ZipIt, which you can download from http://www.maczipit.com/.

After installing an unzipping program, you can decompress any Zip file by opening the program, choosing the Zip file you want to decompress, and then choosing Extract from a toolbar or menu.

One special type of .exe program file is called a self-extracting archive, which is a compressed file or files, just like a Zip file. Unlike a Zip file, however, a self-extracting archive file does not require an unzipping program. Instead, it decompresses itself automatically when you open it (usually by double-clicking). Most large applications offered online, such as Web browsers, download as self-extracting archives.