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 esp. 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.