bit rot

bit rot n.  Also {bit decay}.  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.

   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-detecting circuitry to compensate
   for them).  The notion long favored among hackers that cosmic
   rays are among the causes of such events turns out to be a myth;
   see the {cosmic rays} entry for details.

   The term {software rot} is almost synonymous.  Software rot is
   the effect, bit rot the notional cause.