$U.                      User Interrupt                          Default: $U-

 {$U.}

    Enable interruption of the program at anytime when a Ctrl-C is typed.
    Activation of this directive will slow the program down considerably.

             $U+    Allow user to interrupt program at any point with ^C.

             $U-    Ignore ^C except during I/O (See $C.).

          Range:    From current location to next $U. directive.