File Compression - Computer Education,

 

File Compression
File Compression
Introduction
In computer science and information theory, data compression or source coding is the process of encoding information using fewer bits (or other information-bearing units) than an unencoded representation would use through use of specific encoding schemes.
For example, this article could be encoded with fewer bits if one were to accept the convention that the word "compression" be encoded as "comp." One popular instance of compression with which many computer users are familiar is the ZIP file format, which, as well as providing compression, acts as an archiver, storing many files in a single output file.
As with any communication, compressed data communication only works when both the sender and receiver of the information understand the encoding scheme. For example, this text makes sense only if the receiver understands that it is intended to be interpreted as characters representing the English language. Similarly, compressed data can only be understood if the decoding method is known by the receiver.
Compression is useful because it helps reduce the consumption of expensive resources, such as hard disk space or transmission bandwidth. On the downside, compressed data must be decompressed to be viewed (or heard), and this extra processing may be detrimental to some applications.
For instance, a compression scheme for video may require expensive hardware for the video to be decompressed fast enough to be viewed as it's being decompressed (the option of decompressing the video in full before watching it may be inconvenient, and requires storage space for the decompressed video).
The design of data compression schemes therefore involves trade-offs among various factors, including the degree of compression, the amount of distortion introduced (if using a lossy compression scheme), and the computational resources required to compress and uncompress the data.
By compressing, you "zip" the file so that it is smaller and requires less disk space. Zipping a file is especially helpful if you are planning to send the file as an e-mail attachment or transfer it to another computer.
File Compression
Compressing File with WinZip
Steps
Step One - Open WinZip.
Step Two- Click on the New icon. A window will open displaying the folders on your disk.
Step Three - Move through the folders until you locate the folder where you want to store your compressed file.
Step Four- WinZip creates a file called an "archive." Name your archive.
Step Five- Click Save. You will be returned to the WinZip main window.
Step Six- You must now add a file to the archive that you have just created. Click on Add. A window will open displaying the files and folders on your disk.
Step Seven- Move through the folders until you locate the file that you want to compress. Select that file.
Step Eight- In the compression menu, select the level of compression that you want. The choices may include Normal, None, Fast, Superfast and Maximum.
Step Nine- Add an optional password, if desired.
Step Ten- Click Add. You will return to the main WinZip menu.
Step Eleven- Your compressed file is now added to the archive.
Step Twelve- Close WinZip
Tips & Warnings
• If you have configured your WinZip to display the number of bytes before and after compression, you will be able to see your savings in the WinZip window after you have added the file.
• If you transfer your zipped file (archive) to another computer, the file will not open unless there is a decompression utility installed on that computer.(It doesn't need to be WinZip. Check with your recipient to see what kind of compression software he or she uses and what formats the software can decompress.)
File Compression
Compressing file in Windows XP
Windows XP comes with a built in file compression/ ZIP creation utility. This utility can also be used to Create ZIP Archives and UnZIP zip files.
Creating a ZIP folder with Windows XP
Follow these simple steps to create a ZIP file with Windows XP:
1. Select the file(s)/folder(s) that you want to add to ZIP then Right-Click and select Compressed (zipped) folder from Send To menu from the shortcut menu:
Note: You can use Ctrl+ Click to select multiple files and in case you have multiple files selected then use Ctrl + Right-Click instead of Right-Click
As you can see Windows XP has created a compressed the selected folders in a zip archive.
UnZIPping contents from compressed folder
Follow these steps to unzip content from ZIP archive in Windows XP:
1. Select the archive that you want to UnZip and Right-Click on the archive.
2. Select Extract All option from the shortcut menu.
3. Compressed Folder Extraction Wizard will be displayed. Click on Next to Continue with the wizard.
Select the location where you want to keep the extracted contents and Click on Next to extract the contents.
Wizard has successfully extracted the contents of the ZIP to the selected location, now Click on to complete the wizard and view the extracted contents.