Context diagrams or data flow diagrams are used to illustrate how data is processed by a system. It shows the inputs from the user. Where is the data coming from and how is it being stored. There are two main types of context diagrams. Yourdon and DeMarco notation.
There are two formatting for data flow diagrams and they all look different when displaying information
There are three types of levels to the diagrams. they are each constructed differently. Depending on which level and will look different depending on which level of the system is being used and how the problem and information works. The top level of the context diagram starts at 0. The diagram is presented in a circle showing the system working and how processes work.
the circle represented the process being shown. The Line shows the flow of data between the process and external entity. The external entity is the person or organisation which provides the data to the system. The external entity also receives data from the system.