Login Procedure
Use Case Scenario for a simple ATM system
----------------------------------------------------------------------

The Customer types his PIN number into the Keypad of the ATM machine.
The Little Man reads the PIN number on his Screen, verifies it, then
presents a menu of choices on the User Screen.

[Note that this Use Case is common to both the Deposit and Withdraw
use cases, and so is "used" by both in the graphical notation.]
