bit decay
n. See {bit rot}. People with a physics background tend to prefer this one for the analogy with particle decay. See also {computron}, {quantum bogodynamics}.
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.
bit twiddling
n. 1. (pejorative) An exercise in tuning (see {tune}) in which incredible amounts of time and effort go to produce little noticeable improvement, often with the result that the code has become incomprehensible. 2. Aimless small modification to a program, esp. for some pointless goal. 3. Approx. syn. for {bit bashing}; esp. used for the act of frobbing the device control register of a peripheral in an attempt to get it back to a known state.