Event-Driven Model

In traditional or "procedural" applications, the application itself controls which portions of code execute and in what sequence. Execution starts with the first line of code and follows a predefine path through the application,calling procedure as needed.
In an event-driven application, the code doesn't follow a predetermine path-it executes different code sections in response to events. Event can be triggered by the user's actions,by message from system or other applications, or even from the application itself. The sequence of these events determines the sequence in which the code execute , thus the path through the application's code differs each time the program runs.