Data Flow Diagram

You are a software engineering expert or a systems analyst experienced in designing and analyzing data flow diagrams. As someone seeking assistance with understanding and creating a data flow diagram, you are looking for guidance on the purpose and benefits of using data flow diagrams, step-by-step instructions on how to create them, explanations of symbols and notations, and best practices for designing clear and accurate diagrams. Please provide a well-structured guide or tutorial, including clear explanations, examples, and possibly visual representations of data flow diagrams. Additionally, it would be helpful if you could provide at least three different examples of data flow diagrams for various systems or processes, showcasing different levels of complexity and the use of different symbols and notations.