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Lempel–Ziv–Welch (LZW) compaction An improved form of Lempel–Ziv data compaction. It is provided, for example, as a standard tool in the UNIX operating system. Typically, it achieves compaction ratios approaching 2 for English text, more than 2 for tabulated data text and for source programs, and about 1.5 for binary object programs. Binary data in floating-point notation is almost incompressible owing to the near-random nature of the mantissas.