Event Driven Programming

In computer programming, event-driven programming or event-based programming is a programming paradigm in which the flow of the program is determined by events—e.g., sensor outputs or user actions (mouse clicks, key presses) or messages from other programs or threads.
Event-driven programming can also be defined as an application architecture technique in which the application has a main loop which is clearly divided down to two sections:

• the first is event selection (or event detection)
• the second is event handling.

In embedded systems the same may be achieved using interrupts instead of a constantly running main loop; in that case the former portion of the architecture resides completely in computer hardware

Useful Links:
http://en.wikipedia.org/wiki/Event-driven_programming