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A collection of arcane, unpublished, and (by implication) mostly ad-hoc techniques developed for a particular application or systems area (compare black magic). VLSI design and compiler code optimisation were (in their beginnings) considered classic examples of black art; as theory developed they became deep magic, and once standard textbooks had been written, became merely heavy wizardry. The huge proliferation of formal and informal channels for spreading around new computer-related technologies during the last twenty years has made both the term "black art" and what it describes less common than formerly. See also voodoo programming.