This is the fifth article in the otp introduction series. If you haven’t yet, I recommend you start with the first article which talks about gen_server and lays the foundation for our bank system. If you’re a quick learner, you can read the completed erlang files so far: eb_atm.erl, eb_event_manager.erl, eb_server.erl, eb_sup.erl, and eb_withdrawal_handler.erl.
The Scenario: The ErlyBank system is in a nice state right now with everything wrapped up under the supervisor, but ErlyBank is pressuring us to come up with a package which specifies an overall version so the system can be upgraded as a whole and can be controlled easily. They’ve commissioned us to do this task.
The Result: Erlang/OTP has a built-in module for making a set of modules which achieve some set of functionality into an application. An application can be started and stopped as a unit and can easily be reused in other systems.
