Monday, November 23, 2009

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Secret Of Zip File Format In Windows | ZIP Compression Scheme

ZIP files work somewhat like folders in that they “contain” files, so it’s not surprising that they’re represented as folders in Windows Explorer. But a ZIP file is typically smaller than the sum of its contents, thanks to the ZIP compression scheme.


(Of course, other standards, like RAR, offer much better compression, but Windows doesn’t support .rar files without a third-party utility.)
The late Phil Katz conceived of the ZIP file format at his mother’s kitchen table in 1986, and soon thereafter wrote a little program called PKZip. Although his program, capable of encapsulating and compressing any number of ordinary files and folders into a single archive file, was not the first of its type, it quickly became a standard and ended up revolutionizing the transfer and storage of computer data.
For example, a folder with 10 spreadsheet documents might consume 8 MB of disk space, but when zipped, might only consume 3 MB (or even less). The level of compression varies with the type of data being compressed; zipped text documents can be as small as 4 or 5% of the size of the original source files, but since movies and images are already compressed, they’ll only compress to 95 to 98% of their original size, if that.

This compression makes ZIP files great for sending over the Internet, since smaller files can be sent faster. The ZIP archive format also has built-in error checking, so if you find that certain files are getting corrupted when you email them or send them through a web site, try zipping them up to “protect” them. Zip compression not only protects data being  corrupted, but it also protects your data being affected by virus.

To open a ZIP file, just double-click it. You can extract files from ZIP archives by dragging them out of the ZIP folder window. You can also rightclick a ZIP file and select Extract All, but you’ll have to deal with a more cumbersome wizard interface.

Create a new ZIP file by right-clicking on an empty portion of the desktop or any open folder, and selecting New ➝ Compressed (zipped) folder. (The name here is actually misleading, since ZIP archives are actually files and not folders.) Then, add files or folders to the ZIP by simply dragging them onto the icon or the open ZIP window.

Another way to do this is to right-click a folder or a group of files, select Send To, and then select Compressed (zipped) folder. This is especially convenient, as there’s no wizard or other interface to get in the way: if you send the bench3 folder to a ZIP file, Windows compresses the folder’s contents into a new bench3.zip file, stored alongside the source folder.

All of this is possible because Windows supports the ZIP format right out of the box. (For years, this wasn’t the case because Katz (the founder of zip as said  in the beginning of this post) reportedly despised Windows, which may explain why Windows XP, released a year after his death, was the first version of Windows to support ZIP files without a third-party program.)

Unfortunately, there are drawbacks to Windows Explorer’s built-in support for ZIP files. For example, it can interfere with searches. It can also interfere with third-party ZIP tools like WinZip (http://www.winzip.com), which adds more features and, ironically, better integration with Explorer’s own context menus. But the biggest problem is that, by default, Windows Vista And Windows 7 displays each ZIP file like a folder, which can make a big mess if you have a folder full of ’em.
Unfortunately, there’s no way to get Windows Explorer to treat ZIP files like files without disabling the ZIP feature altogether. But if you want to do it, here’s how... turn off zip support in windows vista | vista secrets.

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About bench3 -

Haja Peer Mohamed H, Software Engineer by profession, Author, Founder and CEO of "bench3" you can connect with me on Twitter , Facebook and also onGoogle+

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