The LZW stands for Lempel–Ziv–Welch. The Lempel–Ziv–Welch is a universal lossless data compression algorithm. It was created by Abraham Lempel, Jacob Ziv, and Terry Welch. It was then published by Welch in 1984. It was an improved implementation of the LZ78 algorithm published by Lempel and Ziv in 1978. According to Wikipedia, the algorithm is simple to implement and has the potential for very high throughput in hardware implementations. The algorithm is used in GIF image format. LZW compression became the first widely used universal data compression method on computers. LZW was used in the public-domain program compress, which became a more or less standard utility in Unix systems around 1986. The scenario described by Welch's 1984 paper encodes sequences of 8-bit data as fixed-length 12-bit codes. According to Wikipedia, The codes from 0 to 255 represent 1-character sequences consisting of the corresponding 8-bit character, and the codes 256 through 4095 are created in a dictionary for sequences encountered in the data as it is encoded. At each stage in compression, input bytes are gathered into a sequence until the next character would make a sequence for which there is no code yet in the dictionary. The code for the sequence (without that character) is added to the output, and a new code (for the sequence with that character) is added to the dictionary.
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