For data compression, the files are compressed and are not usable until you uncompress them. For some programs, you need the same program to uncompress as you used to compress; others are more universal and several other programs have the ability to uncompress.

Some of the benefits of data compression are:

1. reduces the file size as much as 90%
2. the ability to transfer files via email more efficiently
3. saves bandwidth in file transfer
4. the ability to compress your files and archive them to make more room on your hard drive.
5. helps by increasing your computer’s processor speed
6. the ability to add password protection to your files
7. are more resistant to corruption when transferring files

There are a lot of programs available for data compress, some free and some for a nominal cost. Some of the most common compression programs for compressing files for archiving and data transfer are:

PKZIP (.zip)
WinZip (.zip)
StuffIt (.sit)
WinRar
7Zip (.zip)

For a good comparison chart of many of the available file compression programs, check out the article “Comparison of file archivers,” from Wikipedia. The article includes several helpful tables, including General Information (creator, price, etc.); which operating system each compression program will work on; features available, such as password protection, self extraction, file repairing, batch conversion, and encryption. There are also charts which compare which programs will read or write to each other.

You’ll see that ZIP is one of the most universal and StuffIt one of the least.

Another place for useful information is Maximum Compression that has a chart of Compression Programs and gives links for where you can download each program.