The DFD in Figure 3-11 shows the inputs and outputs of the application (payroll processing) as well as the data sources and destinations external to the application. Thus, this context diagram uses rectangles to identify ‘‘Timekeeping’’ and ‘‘Human Resources’’ as external entities, despite the fact that these departments are internal to the company. This is because these entities are external to the payroll processing system under study. The data flow lines connecting these entities to and from the system (e.g., time card data) are called system interfaces.