Using Compressed Data in Windows

There are a variety of programs for working with compressed data in Windows. This article will describe how to use two, at least one of which is available to all SSCC members.

Compression programs look for patterns in the data, and then replace the original file with a file that describes those patterns. Nothing is lost--that description contains all the information needed to recreate the original file. The description will be smaller than the original file, but how much smaller will depend on the data itself and the compression scheme used.

The catch is that it takes CPU time to compress or uncompress a file. Thus compression is really a way to trade CPU power for disk space. For files you use constantly, this may not be a good trade. But we strongly encourage you to compress any data sets you are not using on a regular basis. The SSCC's current disk space was quite costly and we hope to avoid adding to it any sooner than necessary.

Compression Tools Built into Windows XP

If you have Windows XP, compression tools are built right into the operating system. Note that if you have another compression program installed it may take precedence in dealing with compressed files.

To compress a file, right-click on it, choose Send To, and then Compressed (zipped) Folder. The compressed file will be created in the same directory as the original. The original will not be removed, so be sure to delete it or you'll actually be taking up more space! Note that you can also select multiple files, follow the same procedure, and they will be combined into one compressed file.

To uncompress a file, double click on it and a window will open showing its tables. Click File, Extract All.

This will start up the Extraction Wizard. Click Next in the Welcome screen. The next screen will allow you to choose where to save the extracted files--the current location of the compressed file will be entered as a default but you can choose a different location if you prefer. Then click Next.

The final window confirms that the files have been extracted, and gives you the option to open a window showing the extracted files so you can work with them right away.


While the compression tools built in to Windows XP are easy to use, there are many compression programs available with additional features you may want--and if you don't have Windows XP you don't have a choice. We suggest you try IZarc as a free alternative (WinZip and WinRAR are also excellent programs, but they are not free).

Compressing files using IZarc can be done very much like the built-in Windows compression. Select the file(s), right click, and choose IZarc. If you choose to store the files in the new compressed file IZarc suggests, IZarc will take care of the rest automatically, saving the compressed file in the same directory.

Alternatively you can take control of the process by choosing Add to Archive File. This will open an IZarc window where you can choose all sorts of things, including where the compressed file should be stored and the type of compression to use.

To uncompress a file, double-click on it and the IZarc window will open again. To uncompress all the files the compressed file contains, just click Extract.

You'll then be prompted to choose the location where the uncompressed file(s) will be written. You can click on the drop-down menu to quickly choose locations where you've uncompressed files in the past.

Last Revised: 5/10/2006