The document discusses various data compression techniques, including lossless compression methods like Lempel-Ziv (LZ) and Lempel-Ziv-Welch (LZW) algorithms. LZ algorithms build an adaptive dictionary while encoding to replace repeated patterns with codes. LZW improves on LZ78 by using a dictionary indexed by codes. The encoder outputs codes for strings in the input and adds new strings to the dictionary. The decoder recreates the dictionary to decompress the data. LZW achieves good compression and is used widely in formats like PDF.

1. A Review of Data Compression Techniques Presented By IQxplorer

11. The LZW Algorithm (Compression) Flow Chart START W= NULL IS EOF ? K=NEXT INPUT IS WK FOUND? W=WK OUTPUT INDEX OF W ADD WK TO DICTIONARY STOP W=K YES NO YES NO

22. LZW Decompression Algorithm read a character k; output k; w = k; while ( read a character k ) /* k could be a character or a code. */ { entry = dictionary entry for k; output entry; add w + entry[0] to dictionary; w = entry; }

23. LZW Decompression Algorithm Flow Chart START Output K IS EOF ? K=NEXT INPUT ENTRY=DICTIONARY INDEX (K) ADD W+ENTRY[0] TO DICTIONARY STOP W=ENTRY K=INPUT W=K YES NO Output ENTRY