7.1. Programming in an Event-Driven Environment

If you've ever programmed a graphical application using something like Tk or Gtk, you'll know that it's a little different than ordinary procedural programming. In normal programming, you write a sequence of things you'd like the program to do, and it does them. However, GUIs don't work like that—instead, you set up an environment (a window, for instance) that responds to certain events (clicking a button or selecting a menu item). This is called the event-driven paradigm.

It's not just GUIs that use this paradigm. For example, a network server does not do a sequence of events, but it sits waiting for a connection (an event), and then services the connection depending on the input from the client. When the client is done and disconnects, it goes back to waiting for the next event.