Recording the use of system resources. On a multiprogramming system the apportioning of the use of system resources among the active processes can only be done by the system. For resources such as processors, which are allocated in their entirety to an individual process for a large number of short intervals of time, the appropriate measure is found by recording the real time at the start and finish of each interval to give the length of each interval; accumulating these through the life of the process yields the processor time. for resources such as memory, in which a number of subunits is allocated to the process (which will subsequently return them to the resource allocation mechanism), the usually accepted measure is to determine the elapsed time for which the subunits are allocated to the process and to charge a “rent” for each subunit. For nonreusable resources the normal practice is to charge on a unit-cost basis for the amounts used.
In a bureau, which relies for its revenue on real money charges made to clients, the implementation of the accounting system is a nontrivial problem, especially in regard to decisions concerning spoilt work, or delays experienced by one client because of other clients' activities.