Procedures can have an interactive specification that looks like:
(interactive)or
(interactive "%W")This declaration must be the first s-exp after the docstring of a procedure. Primitive procedures may also have interactive specifications and use the SCWM_IPROC macro to support them. The interactive specification marks that a procedure may be invoked interactively (i.e., bound to a mouse or keypress event). The specification also is used to construct the arguments when the procedure is invoked in an interactive context or via call-interactively. The meaning of the various possible substrings in the interactive specification are as follows: