Source : Free On-Line Dictionary of Computing

bit rot
     
         A hypothetical disease the existence of which has
        been deduced from the observation that unused programs or
        features will often stop working after sufficient time has
        passed, even if "nothing has changed".  The theory explains
        that bits decay as if they were radioactive.  As time passes,
        the contents of a file or the code in a program will become
        increasingly garbled.
     
        People with a physics background tend to prefer the variant
        "bit decay" for the analogy with particle decay.
     
        There actually are physical processes that produce such
        effects (alpha particles generated by trace radionuclides in
        ceramic chip packages, for example, can change the contents of
        a computer memory unpredictably, and various kinds of subtle
        media failures can corrupt files in mass storage), but they
        are quite rare (and computers are built with {error detection}
        circuitry to compensate for them).  The notion long favoured
        among hackers that {cosmic rays} are among the causes of such
        events turns out to be a myth.
     
        Bit rot is the notional cause of {software rot}.
     
        See also {computron}, {quantum bogodynamics}.
     
        [{Jargon File}]
     
        (1998-03-15)