The term cost is made specific when it is modified by such descriptions as direct, prime, conversion, indirect, fixed, variable, controllable, product, period, joint, estimated, standard, sunk, or out of pocket. Each modification implies a certain attribute that is important in measuring cost. Each of these costs is recorded and accumulated when management assigns costs to inventories, prepares financial statements, plans and controls costs, makes strategic plans and decisions, chooses among alternatives, motivates personnel, and evaluates performance. The accountant involved it planning and decision making must also work with future, replacement,, differential, and opportunity costs, none of which is recorded and reported in external financial statements.