Tutorial By Marc Hoffman

Problem: An email containing a file with the extension .zip arrives in the email. What is "zip", and what do you do with it?

Solution: Despite the fact that the internet is getting faster (via 56k modems, ISDN, and so forth), saving time on bringing in large amounts of information is still important. So, on large files that are sent via the internet, compression is the key. The smaller the file is the less time it will take to bring into a computer over the internet (via downloading or email). Enter ZIP (this is not to be confused with Iomega's ZIP drive, which is a *completely* different subject). Most files, whether they be graphics, sounds, spreadsheets, Word Documents, or even entire programs, all contain what is termed as redundant information. This redundant information can cause the files to become large. What ZIP does is to eliminate this unused redundant space within files, which can dramatically reduce the files' sizes. This all works without damaging the files' data.

One of the best examples of over bloated sized files is the Windows Bitmap image format. Typically, the file extension on a Windows Bitmap image is ".BMP". BMP images are the native image format that Windows 3.1x, Windows 95, Windows 98, and Windows NT use to store pictures on a computer.  So, to demonstrate the usefulness of ZIP compression and the advantages of ZIP on sending files over the internet, consider the following example, in which we created a test BMP picture.
 
 

Windows BMP Picture File Without ZIP Compression
Windows BMP Picture File With ZIP Compression
1.37 Megabytes
197k (over 80% smaller)
Requires 5.8 Minutes to download over a 56k modem connection
Requires 49.3 Seconds to download over a 56k modem connection
Time savings in downloading a ZIP compressed file is one of ZIP's advantages.

So now that we know why ZIP is such an important means of sending information over the internet, the next question is obvious. Once the file is compressed in ZIP format and you receive the file, how do you get the file back into its original condition so that you can use it (or, in this case, view the picture)? There are a couple of options. First, and the most popular for Windows, is a program appropriately called "WinZIP". WinZIP can be downloaded free on a trial basis (you are expected to pay a registration fee if you use it more than 30 days). WinZIP allows both compression and decompression of files. An added bonus is that when you receive a ZIP file and WinZIP is installed on your computer, all that needs to be done is to double-click on the ZIP file, and WinZIP will open the file giving you options on where you want to decompress it. WinZIP can be downloaded by going to www.winzip.com.

Aladdin Systems, maker of the popular "Stuffit" compression format for the Macintosh, has a program called "Aladdin Expander". This program is free of charge, and will decompress just about every compression format known to exist, including ZIP files as well as Macintosh Stuffit archives. Unlike WinZIP, there is no registration fee, and if you work with both Mac and Windows, this is the way to go. But, this program will only decompress, and will not compress files into ZIP archives. Expander can be downloaded free of change by going to www.aladdinsys.com/expander/index.html.