.NOSHOW   ; Turn off listing file display.  Counter < 0.
           .
           .
           .
        .SHOW     ; Turn on listing file display.  Counter = 0.
                  ; Value of .SHOW options are used.
           .
           .
           .
        .SHOW     ; Counter > 0.  Listing file display is
                  ; on for all options regardless of setting.
           .
           .
           .