How can it do that?

["hzeng" <hzeng hf tvia com>]

Hello,
    I find the interest thing in many example code that you can create many same type of widgets use 
a same widget name, but the system can differ these widgets although they have the same name.

such as:

    Widget *button;
    button=gtk_button_new_with_label("button1");
    gtk_signal_connect(GTKOBJECT(button),"clicked",GTK_SIGNAL_FUNC(callback),(gpointer)"button1");
    ...
    button=gtk_button_new_with_label("button2");
    gtk_signal_connect(GTKOBJECT(button),"clicked",GTK_SIGNAL_FUNC(callback),(gpointer)"button2");
    ...

 At this situation, the system still can know the "clicked" signal is come from button1 or come from button2 and the
callback founction can print different message. I am wondered about these. Can I get the reason?

Thank you very much
Hzeng