Compressing (or zipping) and extracting files on Windows

Compressing is about saving amount of storage space on your computer’s hard drive or other removable storage devices. The amount space that is saved with file compression depends on the type and size of the files being compressed. In general, compressing of text and graphics files yields a high compression ratio than compressing other types of files (such as executable program files).

If you care to know how file compression works, let’s briefly discuss what file compression really does to one or more files. Suppose you have a text file that contains the line:

This is just a test.

Assume you want to compress this file. When you use the file compression software, it basically searches for consecutive occurrences of repetitive characters. The software, for instance, could start by finding at least two consecutive characters it has already seen and replace them with a different value or token. In this sentence, here is the set of two consecutive characters:

is (in This and is) and the following space character
st (in just and st) and the following space character

So essentially our original sentence after file compression could be reduced to just

Th**ju$a te$.

Assume here one star (*) means "is" and a "space" character, and the dollar sign ($) means "st" and a "space" character. The resulting string looks strange as are most tasks to many people. However, the compressing technique reduced the original sentence of 20 characters to just 13 characters. This is not a huge gain in terms of how much memory space is saved for storing this sentence but when this technique is applied to a bigger text file, the amount space saved is more evident.

Of course in the interest of saving storage space you choose to compress the files but this approach should not sacrifice the content of the file. In other words, when you uncompress the files you have compressed, you want to get a file that is similar to what you started with. Otherwise, the technique serves no real use.

The compressing (zipping) and uncompressing (unzipping) algorithms are created and tested to be safe on user’s content. You don’t want to end up with corrupted a data when you use the uncompress function. To be sure, that you can get the original files after compressing, it is useful to test the uncompressed file. How?

There are of course extra steps but they may be worth the trouble if you are compressing important documents or files. Simply, after compressing the files, uncompress the resulting file (folder). Review the uncompressed folder by opening files to see you have not lost any content. If you have not lost any content and your file open normal, you know compressing and uncompressing does not loose any information. So you’re uncompressed file is safe to keep for storage and for later use.

Important note

If you are new to computing or just want to be cautious, always have backup files in case you loose any file in the process of compressing or uncompressing. You may delete the backup files after you are familiar with using file compression technique safely. Remember the files you delete accidentally or intentionally, go in to your computer’s Recycle Bin. If you suspect a file is no longer at your machine, try looking into the Recycle Bin.

Compressing files

This is how you compress the files:

  • Navigate to the folder or file you want to compress
  • Right-click the file or folder
  • Choose Send To and click on "Compressed (zipped) Folder"
Choosing a file to compress
Choosing a file to compress

This should start the compressing process. A small compressing window will close after compressing is done. The compressed folder will appear at the same location where you started the compression process. So if you are compressing a Word document in My Documents, your compressed file will also be in My Documents with the same name as your word document. But then how can you tell them apart? You should see a zipper icon instead of the Word document icon. This is because the compressed file is of type Compressed (zipped) Folder while the Word document is of type "Microsoft Word Document."

Uncompressing files

Uncompressing (unzipping, extracting) the files is also very straight forward process. Simply choose the file you want to extract. You can do this by just clicking once on the Compressed (zipped) Folder. Then, right-click to choose the extract option that suits your preferences. You have number of options when extracting the compressed file. You can extract to the same location. Remember choosing this will replace your uncompressed existing file (if any). Alternatively, you can extract to a different location. So instead of extracting to My Documents, you can extract, for instance, to a folder called sales in My Documents.

Posted on 2/5/2008
by Raj Singh