Software rot, also known as
code rot,
bit rot,
software erosion,
software decay or
software entropy describes the perceived "rot" which is either a slow deterioration of software performance over time or its diminishing responsiveness that will eventually lead to software becoming faulty, unusable, or otherwise called "
legacy" and in need of
upgrade. This is not a physical phenomenon: the software does not actually decay, but rather suffers from a lack of being responsive and updated with respect to the changing environment in which it resides.