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Quick Guide to File Compression

If you have owned your computer for a year or more, you have probably run into the problem of large files, and hard-drive space. The salesman’s promise, “You’ll never use all the space on this computer!”, sounds more and more like so much advertising. Once you actually start to use the computer for more than just the occasional game of solitaire, all of the programs, video games, and assorted emails begin to stack up. Before you know it you may start getting warning messages like, “Hard-drive space is running low. Do you want to clean up some files on your computer?”

Or perhaps you’ve run into a situation where you’ve spent hours working on a report containing lots of graphics, and charts, and some spreadsheets. You go to copy the report to a disk or send it as an email attachment, only to find that it has morphed into a 15 meg monster of a file.

The best way to combat these kinds of file space problems is to utilize a simple compression program. The function of a compression program is to take large files and make them smaller without changing, or losing any information in the file. It does this by using a complex set of algorithms and equations that take the bits of information in the file, reduce the size, and then remember how to put the files back together. Since a file is made up of 1000’s of bits of information it can be reduced from 1000’s down to 100’s without losing information because an algorithm can predict where those other bits WILL go when the file is uncompressed later.

Now of course, like everything in the computer world, there are many different compression programs out there to choose from. Even though each program uses different algorithms for their compression, they all compress files about the same. A typical compression rate for a 100k Word document containing all text is about 60%-90% of the original file size. With this in mind, choosing your own favorite compression utility is usually a matter of personal taste, and ease of use.

One of the most common, and user-friendly programs is called PKZIP. This program is freely available from It’s user interface combines functionality, with ease of use by putting the compression terminology into easy to understand terms.

Another highly used compression utility is called RAR. The RAR compression format is an extremely good one for packing together large programs into one very small file. One of the best features about this particular program is it’s ability to take extremely large files, and spread them out over several smaller files which can be stored on individual floppy disks. This program is also free to the public at
A third extremely popular shareware compressing agent is called ARJ, and can be found at This program has all the same abilities as RAR, and PKZIP, but just in a different format, and file extension.

With the various compression utilities out there, it’s nice to have more than one around so that you can open other people’s files. You can only unzip a file with a .zip extension using PKZIP. A file with the .arj extension can only be opened with ARJ, and the .rar extension consequently can only be opened with the RAR program. Most files on the internet come compressed in one of these three above formats, and some sites even have 3 differently compressed copies for you to choose from all in the place.

The world of compression is an important one, simply for the fact that it allows us a little bit of control over the size of our computers, and the time which we spend downloading one another’s files. So when those files come up that just seem bigger than you can handle, pull out your favorite compression program, and cut it down to size.

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