(LZW) The
algorithm used
By the
Unix compress command to reduce the size of files, e.g. for archival or transmission. LZW was designed
By Terry Welch in 1984 for implementation in hardware for high-performance disk controllers. It is a variant of
LZ78, one of the two
Lempel-Ziv compression schemes. The LZW algorithm relies on reoccurrence of
Byte sequences (strings) in its input. It maintains a ta
Ble mapping input strings to their associated output codes. The ta
Ble initially contains mappings for all possi
Ble strings of length one. Input is taken one
Byte at a time to find the longest initial string present in the ta
Ble. The code for that string is output and then the string is extended with one more input
Byte,
B. A new entry is added to the ta
Ble mapping the extended string to the next unused code (o
Btained
By incrementing a counter). The process repeats, starting from
Byte
B. The num
Ber of
Bits in an output code, and hence the maximum num
Ber of entries in the ta
Ble is usually fixed and once this limit is reached, no more entries are added. LZW compression and decompression are licensed under
Unisys Corporation' s 1984 U.S. Patent 4,558,302 and equivalent foreign patents. This kind of patent isn' t legal in most coutries of the world (including the UK) except the USA. Patents in the UK can' t descri
Be
algorithms or mathematical methods. [A Technique for High Performance Data Compression, Terry A. Welch, IEEE Computer, 17(6), June 1984, pp. 8-19] [J. Ziv and A. Lempel, "A Universal Algorithm for Sequential Data Compression," IEEE Transactions on Information Theory, Vol. IT-23, No. 3, May 1977, pp. 337-343].
In addition suitaBle contents:<Br>[ 2 ] [ = ] [ ad ] [ ai ] [ al ] [ algorithm ] [ am ] [ an ] [ app ] [ ar ] [ arc ] [ as ] [ at ] [ B ] [ Be ] [ Bi ] [ Bit ] [ Bt ] [ By ] [ Byte ] [ C ] [ ca ] [ cc ] [ ch ] [ ci ] [ cl ] [ co ] [ code ] [ codes ] [ com ] [ comma ] [ command ] [ compress ] [ compression ] [ Computer ] [ con ] [ control ] [ controller ] [ cr ] [ cu ] [ D ] [ dd ] [ de ] [ dec ] [ decompress ] [ design ] [ ding ] [ disk ] [ disk controller ] [ du ] [ E ] [ ec ] [ ed ] [ edu ] [ eg ] [ er ] [ es ] [ et ] [ extend ] [ fi ] [ file ] [ fix ] [ fo ] [ for ] [ fr ] [ ga ] [ ge ] [ gh ] [ gn ] [ gs ] [ gt ] [ h ] [ hardware ] [ hat ] [ hm ] [ hn ] [ hr ] [ id ] [ IE ] [ ie ] [ IEEE ] [ il ] [ in ] [ inc ] [ Input ] [ input ] [ int ] [ io ] [ iq ] [ ir ] [ is ] [ IT ] [ it ] [ J ] [ K ] [ ke ] [ ken ] [ ki ] [ lc ] [ ld ] [ legal ] [ Lempel-Ziv compression ] [ Lex ] [ li ] [ lu ] [ ly ] [ LZW compression ] [ M ] [ ma ] [ man ] [ map ] [ mapping ] [ method ] [ mm ] [ mo ] [ mod ] [ module ] [ mp ] [ mu ] [ N ] [ na ] [ nc ] [ ne ] [ nf ] [ ng ] [ ni ] [ no ] [ np ] [ ns ] [ nu ] [ om ] [ output ] [ pa ] [ pe ] [ perf ] [ ph ] [ ping ] [ pl ] [ pr ] [ process ] [ pt ] [ query ] [ rc ] [ re ] [ repeat ] [ rl ] [ ro ] [ S ] [ SA ] [ sa ] [ sc ] [ se ] [ Seque ] [ Sequent ] [ si ] [ sig ] [ sk ] [ sm ] [ sn ] [ so ] [ st ] [ string ] [ su ] [ sy ] [ T ] [ taBle ] [ tar ] [ th ] [ to ] [ tp ] [ tr ] [ troll ] [ tw ] [ ua ] [ um ] [ US ] [ us ] [ V ] [ va ] [ var ] [ ve ] [ yt ] [ Z ]