 Modest Physical CTT is thus formulated in terms of what can be physically computed—more precisely, which functions over a denumerable domain can be physically computed. Prototypical examples of physical computation are the processes of ordinary digital computers and their components, including digital circuits. These processes can be exhaustively described by effective procedures, which are already covered by Mathematical CTT, plus relatively uncontroversial mappings between physical states and computational states. Mathematical CTT says that any function computable by an effective procedure is computable by a TM. As TMs can be physically implemented (or replaced by a computing human), any process that follows an effective procedure is physically computable.