Description Before using GTK+, you need to initialize it; initialization connects to the window system display, and parses some standard command line arguments. The gtk_init() function initializes GTK+. gtk_init() exits the application if errors occur; to avoid this, use gtk_init_check(). gtk_init_check() allows you to recover from a failed GTK+ initialization - you might start up your application in text mode instead. Like all GUI toolkits, GTK+ uses an event-driven programming model. When the user is doing nothing, GTK+ sits in the main loop and waits for input. If the user performs some action - say, a mouse click - then the main loop "wakes up" and delivers an event to GTK+. GTK+ forwards the event to one or more widgets. When widgets receive an event, they frequently emit one or more signals. Signals notify your program that "something interesting happened" by invoking functions you've connected to the signal with g_signal_connect(). Functions connected to a signal are often termed callbacks. When your callbacks are invoked, you would typically take some action - for example, when an Open button is clicked you might display a GtkFileSelectionDialog. After a callback finishes, GTK+ will return to the main loop and await more user input. It's OK to use the GLib main loop directly instead of gtk_main(), though it involves slightly more typing. See GMainLoop in the GLib documentation.