Source code in the pl/i programming language

tower: proc options (main);

   call Move (4,1,2,3);

Move: procedure (ndiscs, from, to, via) recursive;
   declare (ndiscs, from, to, via) fixed binary;

   if ndiscs = 1 then
      put skip edit ('Move disc from pole ', trim(from), ' to pole ',
         trim(to) ) (a);
   else
      do;
         call Move (ndiscs-1, from, via, to);
         call Move (1, from, to, via);
         call Move (ndiscs-1, via, to, from);
      end;
end Move;

end tower;