Whereas document flowcharts focus on tangible documents, system flowcharts concentrate on the computerized data flows of AISs. Thus, a system flowchart typically depicts the electronic flow of data and processing steps in an AIS. Figure 3-5 illustrates some common system flowcharting symbols. Most of these symbols are industry conventions that have been standardized by the National Bureau of Standards (Standard × 3.5), although additional symbols are now necessary to represent newer data transmission technologies—for example, wireless data flows.