diff --git a/xtandard.h b/xtandard.h
index 50c0351..fb8b6c4 100644
--- a/xtandard.h
+++ b/xtandard.h
@@ -35,6 +35,17 @@ enum {
 	COLOUR_COUNT
 };
 
+enum {
+	SIGNAL_NONE,
+	SIGNAL_A,           SIGNAL_B,           SIGNAL_C,           SIGNAL_D,           SIGNAL_E,           SIGNAL_F,           SIGNAL_G,           SIGNAL_H,
+	SIGNAL_I,           SIGNAL_J,           SIGNAL_K,           SIGNAL_L,           SIGNAL_M,           SIGNAL_N,           SIGNAL_O,           SIGNAL_P,
+	SIGNAL_Q,           SIGNAL_R,           SIGNAL_S,           SIGNAL_T,           SIGNAL_U,           SIGNAL_V,           SIGNAL_W,           SIGNAL_X,
+	SIGNAL_Y,           SIGNAL_Z,           SIGNAL_0,           SIGNAL_1,           SIGNAL_2,           SIGNAL_3,           SIGNAL_4,           SIGNAL_5,
+	SIGNAL_6,           SIGNAL_7,           SIGNAL_8,           SIGNAL_9,           SIGNAL_SPACEBAR,    SIGNAL_TABULATOR,   SIGNAL_RETURN,      SIGNAL_NEW_LINE,
+	SIGNAL_SLASH,       SIGNAL_BACKSLASH,   SIGNAL_QUOTE,       SIGNAL_BACKQUOTE,   SIGNAL_BACKSPACE,   SIGNAL_ESCAPE,      SIGNAL_CONTROL,     SIGNAL_SHIFT,
+	SIGNAL_COUNT
+};
+
 extern char * program_name;
 extern char * program_mode;
 extern char * program_license;