Zipping and Compression

Windows XP supports two very different kinds of file compression. The distinction is confusing but important, so bear with me. File compression reduces the size of a file by cleverly taking out parts of the contents of the file that aren’t needed, storing only the minimum amount of information necessary to reconstitute the file extract it into its full, original form. A certain amount of overhead is involved, because the computer has to take the time to squeeze extraneous information out of a file before storing it, and then the computer takes more time to restore the file to its original state when someone needs the file. But compression can reduce file sizes enormously. A compressed file often takes up half its original space even less, in many cases. How does compression work? That depends on the compression method you use. In one kind of compression, known as Huffman encoding, letters that occur frequently in a file (say, the letter e in a word processing document) are massaged so that they take up only a little bit of room in the file, while letters that occur less frequently (say, x) are allowed to occupy lots of space. Instead of allocating eight 1’s and 0’s for every letter in a document, say, some letters may take up only two 1’s and 0’s, while others could take up 15. The net result, overall, is a big reduction in file size. It’s complicated, and the mathematics involved gets quite interesting. Windows XP’s two file compression techniques are as follows:  -  Files can be compressed and placed in a “Compressed (zipped) Folder,” with an icon to match.  -  Files, folders, or even entire drives can be compressed using NTFS’s built-in compression capabilities. Here’s where things get complicated. NTFS compression is built into the file system: You can use it only on NTFS drives, and the compression doesn’t persist when you move (or copy) the file off the drive. Think of NTFS compression as a capability inherent to the disk drive itself. That isn’t really the case Windows XP does all the sleight-of-hand behind the scenes but the concept will help you remember NTFS compression’s limitations and quirks. Although Microsoft would have you believe that Compressed (zipped) Folder compression is based on folders, it isn’t. A Compressed (zipped) Folder is really a file not a folder but it’s a special kind of file called a Zip file. If you’ve ever encountered Zip files on the Internet (they have a filename extension of .ZIP and they’re frequently manipulated with programs such as WinZip, www.winzip.com), you know exactly what I’m talking about. Zip files contain one or more compressed files, and they use the most common kind of compression found on the Internet. Think of Compressed (zipped) Folders as being Zip files, and if you have even a nodding acquaintance with ZIPs, you’ll immediately understand the limitations and quirks of Compressed (zipped) Folders. Microsoft calls them Folders because that’s supposed to be easier for users to understand. You be the judge. If you try to compress the drive that contains your Windows folder, you won’t be able to compress the files that are currently in use by Windows. To use NTFS compression on an entire drive, follow these steps:

1. Make sure that you are a full-fledged Administrator (see Article I, Article 6).

2. Choose Start -> My Computer and right-click the drive that you want to compress. Click Properties and click on the General tab 3. If the drive is formatted with NTFS, you see a check box saying Compress Drive to Save Disk Space. Select this check box. 4. Click OK. Windows asks you to confirm that you want to compress the entire drive. Windows takes some time to compress the drive in some cases, the estimated time is measured in days. Good luck. To use NTFS compression on a folder or single file, follow these steps:

1. Make sure that you are a full-fledged Administrator.

2. Navigate to the folder or file you want to compress (for example, choose Start -> My Documents or Start -> My Computer). Right-click on the file or folder you want to compress. Click Properties and click the Advanced button on the General tab. 3. Select the Compress Contents to Save Disk Space check box and click OK. To uncompress a file or folder, go back into the Advanced Properties dialog box (right-click the file or folder, click Properties, and then click Advanced) and deselect the Compress Contents to Save Disk Space check box. To use Zip compression, er, Compressed (zipped) Folders, you must first create a Zip file, er, a Compressed (zipped) Folder. Here’s how:

1. Choose Start -> My Documents to navigate to the folder that you want to contain your new Zip file.

2. Right-click in any convenient empty location within the window and choose New -> Compressed (Zipped) Folder. Windows responds by creating a new Zip file, with a .ZIP filename extension, and placing it in the current folder. The new file is just like any other file you can rename it, copy it, move it, delete it, send it as an e-mail attachment, save it on the Internet, or do anything else to it that you can do to a file. (That’s because it is a file.)

3. To add a file to your Compressed (zipped) Folder, simply drag it onto the zipped folder icon.

4. To copy a file from your Zip file (uh, folder), double-click the zipped folder icon, and treat the file the same way you would treat any regular file.

5. To copy all of the files out of your Zip file (folder), click Extract All Files in the Folder Tasks Pane. You see the Windows XP Compressed (zipped) Folders Extraction Wizard, which guides you through the steps. The Compressed (zipped) Folders Extraction Wizard places all the copied files into a new folder with the same name as the Zip file which confuses the living bewilickers out of everybody. Unless you give the extracted folder a different name from the original Compressed (zipped) Folder, you end up with two folders with precisely the same name sitting on your desktop. Do yourself a huge favor and feed the wizard a different folder name while you’re extracting the files.