Understanding File Compression and Archives

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When to use an archive or file compression

Now that you know what a compressed file or an archive is, you must be asking yourself why you would want to use them. The three most common reasons to use archives and compressed files are:

File compression saves storage space

By using a compressor to make an image smaller, you are using up less space on your hard drive to store this file. For example, a word document that is 89 Kilobytes on my hard drive, when zipped, is now only 8 Kilobytes. That is a 90% saving in storage space! Take a look at the table below to see some more examples of the type of storage space you can save using file compression:

As you can see, some file formats compress a great deal more than other formats. This is because certain file types are already compressed, and therefore can not be compressed any further. Looking at the chart above, it obviously does not make sense to compress MP3, GIF, JPEG, or other compressed file formats as you will not gain any benefit. On the other hand, Word, Excel, Text, and program files compress quite well

Transmission Speeds

How fast a file is transmitted over a network or the Internet is dependent upon how big this file is. For example, a file with the size of 1,337,344 bytes took approximately 28 seconds to upload to a remote server. Yet this same file compressed to a size of 554,809 bytes only took 12 seconds. That is a savings in time of over 50%. Now imagine you were sending files that would normally take an hour to send, and after compressing the files, it now only takes 30 minutes. The savings in time and potentially money is incredible.

Sending only 1 file

There are times that you need to send many attachments in one email message. This can be difficult and confusing at times, so instead you use an archival program to convert the 20 files into a single file. This is much more organized and easier to manipulate.

Backing up data

Archival programs are used often to back up data. You would use archives to backup a folder or a number of files into a single file and compress them as well. This allows you to save space and then store that individual file on a floppy or other removable media.

Note: It is important to note though, that with all formats, whether it be a compressed file or an archive, you must always uncompress and/or extract the file before you will be able to use it.

Types of archives and file compressors

There are many types of archival progarms and compressors. The table below will give a listing of the more common programs that are used today along with the file extension that they use:

* Many of these programs can handle more than one format. The format listed is the native format for that program.

** The operating system listed is the native operating system for these formats. These formats may be able to be used on other operating systems as well.

Conclusion

Now that you understand file compression and archiving, download some of the above programs and play around with them. They are very easy to use and understand. For detailed instructions on creating Zip files, visit the following tutorials:

How to create and extract a Zip File in Windows ME/XP/2003

How to create and extract a ZIP File in Windows 95/98/2000

As always, if you have any questions, please feel free to ask them in the computer help forums.

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Lawrence Abrams
Bleeping Computer Basic Computer Concept Tutorial Series
BleepingComputer.com: Computer Help & Tutorials for the beginning computer user.