Context diagram: An overview of an organizational system that shows the boundaries of the system, the external entities that interact with the system and the main flows of information between the entities and the system. In this diagram, a single process represents the complete system.
First level DFD: A data flow diagram that represents the main processes, data flows and data stores of a system with a high level of detail.
Draw the DFDs up to the 2nd level for the Online Exam System.