Planned systemic obsolescence is the deliberate attempt to make a product obsolete by altering the system in which it is used in such a way as to make its continued use difficult. Common examples of planned systemic obsolescence include not accommodating forward compatibility in software, or routinely changing screws or fasteners so that they cannot easily be operated on with existing tools. This may either be designed to intentionally cause obsolescence, or by interface standards being superseded by better standards that were not available when the product was designed, such as serial ports, parallel ports, and PS/2 ports largely being supplanted or replaced by USB on newer PC motherboards in the 2000s.