 Switching circuit theory became the foundation of digital circuit design, as it became widely known in the electrical engineering community during and after World War II, with theoretical rigor superseding the "ad hoc" methods that had prevailed previously.Metal-oxide-semiconductor (MOS) logic originates from the MOSFET (metal-oxide-semiconductor field-effect transistor), invented by Mohamed M. Atalla and Dawon Kahng at Bell Labs in 1959.They first demonstrated both PMOS logic and NMOS logic in 1960.