1.What is the DFD Level 0 Diagram?
-In this diagram, the system will be divided into processes as 1.0 2.0 3.0 4.0 5.0
-In the level 0 diagram, we will visualize the data flow between the data sources, data stores and processes

2.Element of Level 0 Diagram
2.1 Data Source
-The data source is visualized as non rounded rectangle
-The data source is usually as a person or an entity where the data initialize
2.2 Data
-This is the data flow from/to data source to processes.
2.3 Process
-It is visualized as system 0. A process comes with rounded rectangle, process number and the process name
-The name of the process is Verb or Verb Phrase
2.4 Data Store
-Data store is visualized as the horizontal rectangle
-The data store number is denoted as D1 D2 D3
-The name of the data store is followed to the syntax data+”File”. For example, data is book, so the data store is book file

3.Relationship
-We draw arrows to indicate the data flow between data source, process, data store
-We need to clearly define the data that is transferred in the arrow
-THE RELATION NEED TO FOLLOW THE DFD VIOLATION RULE

4.Step to draw a DFD Context Diagram
-Try to list the data source, process and data store in a proper order that meet the VIOLATION
-Draw the flow and indicate the data

App A: Note
-The data must be N/N Phrase
-NEED TO FOLLOW THE VIOLATION FOR DATA SOURCE, PROCESS AND DATA STORE
-The diagram must be start with a data source

App: Sample
https://prestobear.com/2018/05/case-study-mortgage-rate-quote-system/