@code{tooltip-gud-tips-p} to @code{t}. Then you can display a
variable's value in a tooltip simply by pointing at it with the mouse.
In graphical mode, with a C program, you can also display the #define
-directive assiciated with an identifier when program is not executing.
+directive associated with an identifier when program is not executing.
This operates in the GUD buffer and in source buffers with major modes
in the list @code{tooltip-gud-modes}.