#include <X11/Intrinsic.h>// To define the constant 'XtNcallback':#include <X11/StringDefs.h>// Definition of the Athena List Widget:#include <X11/Xaw/List.h>void do_list_item_selected(Widget w, XtPointer unused, XtPointer data) {  XawListReturnStruct *list_item = (XawListReturnStruct*)data;  printf("Selected item (%d) text is '%s'\n",         list_item->list_index, list_item->string );}int main(int argc, char **argv) {  Widget top_level, list;  XtAppContext application_context;  String items[] = {    "1", "2", "3", "4", "5", "six", "seven", "8",    "9'th list entry", "this is the tenth list entry",    "11", "12",    NULL  };  top_level = XtAppInitialize(&application_context, "listexample",			      NULL, 0,			      &argc, argv, NULL,			      NULL, 0);  list= XtVaCreateManagedWidget("list",  listWidgetClass, top_level,				XtNlist, items,				NULL, 0);  XtAddCallback(list, XtNcallback, do_list_item_selected, (XtPointer)NULL);      XtRealizeWidget(top_level);  XtAppMainLoop(application_context);  return 0;a}