SOFTWARE ENGINEERING

Detailed explanation-1: -There are four symbols in the DFD language, that is, processes, data flows, data stores, and external entities, each of which is represented by a different graphic symbol. An external entity sends or receives data from the system. It is represented by a rectangle.

Detailed explanation-2: -In DFD, an input/output receiver is generally represented by a rectangle.

Detailed explanation-3: -A context diagram, sometimes called a level 0 data-flow diagram, is drawn in order to define and clarify the boundaries of the software system. It identifies the flows of information between the system and external entities. The entire software system is shown as a single process.

Detailed explanation-4: -An external entity sends or receives data from the system. It can represent a person, a machine, an organization etc., that is external to the system being modeled. Flows outgoing from external entities go to processes.