Describing in detail what each of the FOUR (4) symbols used in a DFD represents.


  • An external entity is a source or recipient of data outside of the system boundary.

  • A process indicates that some activity is taking place on the data.

  • All decisions occur within the process.

  • A data store is a repository of data that may be accessed or changed.

  • Data stores can be physical or electronic files, people, the Internet, etc.

  • Data flows show how data flows between the other entities and has an arrow to show direction.