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Beginning Programming ALL-IN-ONE DESK REFERENCE FOR DUMMIES® by Wallace Wang

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Chapter IV.4. Data Compression Algorithms

The main idea behind data compression is to shrink information, which takes up less space. Not only does compressed data take up less storage space, but it also takes less time to transfer.

Here are two types of data compression algorithms - lossless and lossy.

With lossless compression, the algorithm can compress the data without losing any information, which is used for archiving and compressing multiple files into a single file, such as a ZIP archive. Think of lossless compression as a way to pack existing data more efficiently, like refolding clothes to make them fit in a suitcase.

With lossy compression, the algorithm actually loses some information to compress data. Typically, this lost information isn't noticed anyway. The most common examples of lossy compression involve MP3 audio files and video files. When compressing audio, the MP3 standard throws out the audio parts that the human ear can't distinguish. When compressing video, compression algorithms toss out colors that the human eye doesn't notice. By throwing out information, lossy compression algorithms can save space, much like throwing away clothes to make packing the remaining clothes in a suitcase easier.

Because lossy compression throws out data, it can compress the same data much smaller than lossless compression. However, lossy compression has only limited use. You wouldn't want to use lossy compression when storing documents because you can't afford to lose any data, for ...

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