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Old software (especially applications) which one is obliged to remain compatible with, or to maintain. DP types call this "legacy code", a term hackers consider smarmy and excessively reverent. The term implies that the software in question is a holdover from card-punch days. Used especially when referring to old scientific and number crunching software, much of which was written in Fortran and very poorly documented but is believed to be too expensive to replace. See fossil; compare crawling horror.