How are activity diagrams used in describing the context of use of a system?

How are activity diagrams used in describing the context of use of a system?
Answer: Activity diagrams are intended to show the activities that make up a system process and the flow of control from one activity to another. The start of a process is indicated by a filled circle and the end by a filled circle inside another circle. In a UML activity diagram, arrows represent the flow of work from one activity to another. A solid bar is used to indicate activity coordination.