CS101.Lect13.Compression.ppt

CS101.Lect13.Compression.ppt - CS101 Lecture 13: Data...

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Computer Science CS101 Lecture 13: Data Compression Keyword Encoding Run-Length Encoding Huffman Encoding Aaron Stevens (azs@bu.edu) 6 October 2011 Computer Science Compress them! How do you fit more cars on this lot? Data compression Reduction in the amount of space needed to store a piece of data.
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Computer Science Compression Strategies Data compression techniques can be: lossless , which means the data can be retrieved without any loss of the original information lossy , which means some information may be lost in the process of compaction Computer Science Example: Text Compression Problem: Unicode assigns 16 bits to each character in a document; uses a heck of a lot of space. We need ways to store and transmit text efficiently. Why? Common lossless compression techniques: keyword encoding run-length encoding Huffman encoding
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Computer Science Keyword Encoding Replace frequently used words with a single character Computer Science Keyword Encoding Example Given the following paragraph, We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness. That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of
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This note was uploaded on 12/16/2011 for the course CS 101 taught by Professor Stevens during the Fall '08 term at BU.

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CS101.Lect13.Compression.ppt - CS101 Lecture 13: Data...

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