Source : Free On-Line Dictionary of Computing

bit twiddling
     
        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
        becomes incomprehensible.
     
        2. Aimless small modification to a program, especially for
        some pointless goal.
     
        3. {bit bashing}, especially used for the act of frobbing the
        device control register of a peripheral in an attempt to get
        it back to a known state.
     
        [{Jargon File}]