The Completed Code for Our Project

#include <gtk/gtk.h>

GtkWidget   *label;
GtkWidget   *entry;
GtkWidget   *list;

static char *titles[] = {
	"Date",
	"Todo item for that day."
};

void
quit_function(
)
{
	exit();
}

void
print_date(
	GtkWidget	*src,
	gpointer		user_data
)
{
	char		buf[256];
	int		month, day, year;
	char		row_data[2][512];
	char		*rows[2];
	char		*todo_text;
	int		row;


	/* Get the date from the calendar */
	gtk_calendar_get_date(GTK_CALENDAR(src), &year, &month, &day);
	sprintf(buf, "%02d/%02d/%d", month+1, day, year);

	/* Get the todo entry */
	todo_text = gtk_editable_get_chars(GTK_EDITABLE(entry), 0, -1);

	/* Place the date into the Todo date along with the Todo entry */
	sprintf((char *)row_data[0], buf);
	sprintf((char *)row_data[1], todo_text);
	rows[0] = row_data[0];
	rows[1] = row_data[1];
	row = gtk_clist_prepend(GTK_CLIST(list), rows);

	/* Update the date label above the calendar */
   gtk_label_set_text(GTK_LABEL(label), buf);

	/* Cleanup */
	g_free(todo_text);
}

int
main(
   int   argc,
   char  **argv
)
{
   GtkWidget   *window;
   GtkWidget   *hbox;
   GtkWidget   *vbox;
   GtkWidget   *cal;
   GtkWidget   *quit;

   /* GTK initialization - required of every GTK program */
   gtk_init(&argc, &argv);

   /* This establishes the top-level window, the parent of all other windows */
   window = gtk_window_new(GTK_WINDOW_TOPLEVEL);

	/* Add a HBox, to handle horizontal layout, inside the top-level window. */
   hbox = gtk_hbox_new(FALSE,0);
   gtk_container_add (GTK_CONTAINER (window), hbox);

	/* Add a VBox, to handle vertical layout, inside the hbox. */
   vbox = gtk_vbox_new(FALSE,0);
   gtk_container_add (GTK_CONTAINER (hbox), vbox);

	/* A List for each days Todo */
   list = gtk_clist_new_with_titles(2, titles);
   gtk_container_add (GTK_CONTAINER (hbox), list);
	gtk_clist_set_column_width(GTK_CLIST(list), 0, 140);
	gtk_clist_set_column_width(GTK_CLIST(list), 1, 240);

	/* A label gets added to the Vbox first. */
   label = gtk_label_new("Date Chosen:  None.");
   gtk_container_add (GTK_CONTAINER (vbox), label);

	/* The Calendar widget does most of the hard work for us */
   cal = gtk_calendar_new();

	/* Add the callback when a new date is chose */
	gtk_signal_connect (GTK_OBJECT (cal), "day_selected",
		GTK_SIGNAL_FUNC (print_date), (gpointer)0);

   /* Place it after the label and inside our vertical layout box */
   gtk_container_add (GTK_CONTAINER (vbox), cal);

	/* A text entry field for adding a note to each date */
   entry = gtk_entry_new();
   gtk_container_add (GTK_CONTAINER (vbox), entry);

	/* A Quit button, to exit gracefully */
   quit = gtk_button_new_with_label("Quit");
   gtk_container_add (GTK_CONTAINER (vbox), quit);

	/* Add the callback for the Quit button */
	gtk_signal_connect (GTK_OBJECT (quit), "clicked",
		GTK_SIGNAL_FUNC (quit_function), (gpointer)0);

   /* And display all the windows */
   gtk_widget_show(quit);
   gtk_widget_show(entry);
   gtk_widget_show(cal);
   gtk_widget_show(label);
   gtk_widget_show(list);
   gtk_widget_show(vbox);
   gtk_widget_show(hbox);
   gtk_widget_show(window);

   /* This is a main loop that all simple GTK applications go into. */
   gtk_main();

   return(0);

}