Compressed files are used for electronic file transfers because they significantly cut your downloading time (in half or even less) and you only have to download one file instead of the many files it often takes to run a program. File compression also makes it possible to fit large collections of files onto one floppy disk.

File compression works on a combination of a few basic principles such as tokenizing, elimination of repetition, and pattern identification combined with some very clever mathematics. There are two basic types of compression: "lossless" and "lossy". Lossless compression is used on program and datafiles. This ensures that the files you get out of the archive are identical to the originals. Lossy compression can give much higher compression ratios, but you cannot guarantee that the decompressed file will match the original. For programs and data, this could be disastrous. Thus, lossy compression is used for image and audio files, where a few missed bits will not be important. For example, JPEG files use a lossy compression.

In order to decompress a .ZIP file like we use on our site, you need a copy of the current version of PKUNZIP, which is a shareware program included with the PKZip package. If you do not have a copy, click here to find a download site for it. If you need help on downloading, see our Downloading basics page.

The PKZip package is a self extracting archive, so before you use it the first time, you must decompress it:

• First, create a subdirectory on your hard drive, such as C:\ZIP, then copy the PKZip program archive you just downloaded (such as PKZ204G.EXE) to that directory. Then,

• In DOS:
  • change to the C:\ZIP directory; then
  • execute the file like a program by typing in its name, such as:
    PKZ204G <enter>

• In WINDOWS 3.x File Manager, or Win'95 Explorer:
  • move the PKZip program archive to the C:\ZIP directory if it is not there already; then
  • double-click on that program to decompress it.

• First, create a directory on your hard drive for the file you want to unZIP. (such as C:\MAXI)
• Next, copy the .ZIP file to that directory.
• Change to the directory.
• Run the PKUNZIP program. Since PKUNZIP is a DOS application/utility, it is best to run it from a C:> DOS prompt. The basic command is PKUNZIP file.zip. For example, if you were unZIPing our MAXI Disk program (MDISK42.ZIP), the command would be:
  PKUNZIP MDISK42 <enter>
  That's all there is to it!

• Using Windows 3.x FileManager or Win'95/NT WindowsExplorer to associate the ZIP file extension with the WinZip application; then
• Double click on the selected ZIP file from Windows 3.x FileManager or Win'95/NT WindowsExplorer;

• Use Windows 3.x FileManager or Win'95/NT WindowsExplorer to drag the ZIP file over to the WinZip icon.

• CCZip
• eZip
• FastZip
• PowerZip
• SimpleZip
• Stuffit expander for Windows
• TurboZip
• ZipMagic
• ZipPlus
• Zvet