If you download many programs and files off the Internet, you've probably encountered ZIP files before. This compression system is a very handy invention, especially for Web users, because it lets you reduce the overall number of bits and bytes in a file so it can be transmitted faster over slower Internet connections, or take up less space on a disk. Once you download the file, your computer uses a program such as WinZip or Stuffit to expand the file back to its original size. If everything works correctly, the expanded file is identical to the original file before it was compressed.
At first glance, this seems very mysterious. How can you reduce the number of bits and bytes and then add those exact bits and bytes back later? As it turns out, the basic idea behind the process is fairly straightforward. In this article, we'll examine this simple method as we take a very small file through the basic process of compression.
Most types of computer files are fairly redundant -- they have the same information listed over and over again. File-compression programs simply get rid of the redundancy. Instead of listing a piece of information over and over again, a file-compression program lists that information once and then refers back to it whenever it appears in the original program.
As an example, let's look at a type of information we're all familiar with: words.
In John F. Kennedy's 1961 inaugural address, he delivered this famous line:
"Ask not what your country can do for you -- ask what you can do for your country."
The quote has 17 words, made up of 61 letters, 16 spaces, one dash and one period. If each letter, space or punctuation mark takes up one unit of memory, we get a total file size of 79 units. To get the file size down, we need to look for redundancies.
Immediately, we notice that:
"ask" appears two times
"what" appears two times
"your" appears two times
"country" appears two times
"can" appears two times
"do" appears two times
"for" appears two times
"you" appears two times
Ignoring the difference between capital and lower-case letters, roughly half of the phrase is redundant. Nine words -- ask, not, what, your, country, can, do, for, you -- give us almost everything we need for the entire quote. To construct the second half of the phrase, we just point to the words in the first half and fill in the spaces and punctuation.
We'll look at how file-compression systems deal with redundancy in more detail in the next section
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- Power Buzzer
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- Try...Super Fast Shutdown
- Try...Super Fast Shutdown
- Simple Flaher Circuit Diagram (24V)
- New Extreme Keyboard
- New Extreme Keyboard
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- New High Quality Printers
- Apple iOS Vs Google ANDROID
- Apple iOS Vs Google ANDROID
- Google Launches Google’s ebookstore
- Google Launches Google’s ebookstore
- Blinking LED Circuit Diagram
- How Restore Missing Folder without Tools
- How Restore Missing Folder without Tools
- Did You Know..???? Most sophisticated computer T...
- Did You Know..???? Most sophisticated computer T...
- TIPS for Computer fast and stable
- TIPS for Computer fast and stable
- WHAT Is Blu-ray Disc...??
- WHAT Is Blu-ray Disc...??
- The 2011 Computer Technology Preview...!
- The 2011 Computer Technology Preview...!
- Wow ...LAtest Technology Intel predicts 10GHz chip...
- Wow ...LAtest Technology Intel predicts 10GHz chip...
- Download Free Windows 7 Harry Potter Themes
- Download Free Windows 7 Harry Potter Themes
- Beware Worm Spread via spam on Facebook and MySpace
- Beware Worm Spread via spam on Facebook and MySpace
- Backup Your drivers with DriverMax
- Backup Your drivers with DriverMax
- How Disable hibernation and remove hiberfil.sys
- How Disable hibernation and remove hiberfil.sys
- How Fix NTLDR is missing error on Windows
- How Fix NTLDR is missing error on Windows
- Introduction to Android
- Introduction to Android
- Repair CD/DVD ROOM and Troubleshoting
- Repair CD/DVD ROOM and Troubleshoting
- Microsoft Releases Research Site HTML5
- Microsoft Releases Research Site HTML5
- Hiding IP Address By SwitchProxy
- Hiding IP Address By SwitchProxy
- Conducting Remote Desktop Connection With TeamViewer
- Conducting Remote Desktop Connection With TeamViewer
- Disable Autorun On USB
- Disable Autorun On USB
- Trusting Password: Network Authentication
- Trusting Password: Network Authentication
- To Ignorant Others With Netbus
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- How to Get Many Visitors Blog / Web Site Free Goog...
- JDownloader, Free Download Manager
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- Download AVG Antivirus Free Edition 2011 (Offline ...
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- Winstep Nexus, Docking System For Windows
- Winstep Nexus, Docking System For Windows
- Provide Variety Of Effects To Photos By FunPhotoBo...
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- Download Free McAfee Internet Security 2011
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- UltraCopier, Enhance Copy Function In Windows
- UltraCopier, Enhance Copy Function In Windows
- Change File Format Online
- Change File Format Online
- Reading Books & Magazines Online With GooReader
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- Fishbowl, Up Client Application
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- VOIP phone system working
- Now is VOIP Phone era
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- How GPS Receivers Work
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- How File Compression Works ...?
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- Duplicate Website and run offline
- Duplicate Website and run offline
- Install Windows From USB Flasdisk
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- How To Reset Printer Canon MP258
- How UPC Bar Codes Work ( Read BARCOCE)
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