diff --git a/compiler/cpp/src/globals.h b/compiler/cpp/src/globals.h
index db7e392..7385565 100644
--- a/compiler/cpp/src/globals.h
+++ b/compiler/cpp/src/globals.h
@@ -3,13 +3,20 @@
 
 class t_program;
 
-/** Global variable: the master program parse tree */
+/**
+ * The master program parse tree. This is accessed from within the parser code
+ * to build up the program elements.
+ */
 extern t_program* g_program;
 
-/** Global debug state */
+/**
+ * Global debug state
+ */
 extern int g_debug;
 
-/** Global time string */
+/**
+ * Global time string, used in formatting error messages etc.
+ */
 extern char* g_time_str;
 
 #endif