This group of statements defines the selections under Scroll on the menu bar. If the quoted string in the ITEM statement is not a valid command, the SELECTION= option corresponds to a subsequent SELECTION statement, which specifies a valid command. 
      menu s;
         item 'Next Obs' selection=n;
         item 'Prev Obs' selection=p;
         item 'Top';
         item 'Bottom';
         selection n 'forward';
         selection p 'backward';