Rules.ini is a configuration file that included unit stats starting from Red Alert. It allows easy modifications because it was not hard-coded as in Tiberian Dawn. Some special programs like TibEd or Red Alchemist are specialised in modifying these values in an annotated manner with selection boxes showing the allowed values to aid new modders. Expansion packs used differently named files that served the same purpose, e.g. aftrmath.ini, firestrm.ini or rulesmd.ini. As of Generals, a unique Rules file is no longer used. Instead, it is split into several parts.