This format code is used to augment the system menu and is constructed in a
manner similar to %mn - Menu. A grave accent modifier (`) is used in order to replace
the menu rather than to add to it.
will add the menu items Alpha and Beta to the end of the system menu. Beta will
be greyed when the control variable Beta_cntrl has a zero value. Alpha_func
and Beta_func are the associated call-back functions. If a grave accent
is supplied in the form %`sm, then the two menu items will replace the system
The tab character CHAR(9) (or CHAR(20)) attaches an accelerator key to a
particular menu item and its associated call-back function. The syntax is the
same as that for %mn above.