UML use case diagrams are the primary form of system/software requirements for new software programs under development. Use cases specify the expected behavior (what), not the exact method (how) to make it happen.
Once a use case is specified, it can be represented in a textual and visual representation (i.e., a use case diagram).
A key concept of use case modeling is that it helps us design a system from the end user's perspective.
It is an effective technique to communicate system behavior in user terms by specifying all externally visible system behaviors.
ATMs enable customers or users to perform financial transactions. These transactions can be performed in a public space without any clerk, cashier or bank teller. With the help of use case diagrams, the working and description of ATMs can be easily explained as shown in the example.
