shared variable between tasks

[tancheeh@fred.cs.washington.edu (Nicholas Tan Chee Hiang)]

I am trying to understand concurrency in Ada.  Can someone please tell
me why the variable Unprotected below is never updated?  Thanks!

- N

------------------------------>code below<------------------------------

with Text_IO;  use Text_IO;

procedure Unprotected_Shared_Variable is
  Unprotected : Character := '*';
  pragma SHARED(Unprotected);

  task Write_Letter_A_To_Variable;
  task Access_Variable;

  task body Write_Letter_A_To_Variable is
    Letter : constant Character := 'A';
  begin
    loop
      Unprotected := Letter;
      delay 0.5;
    end loop;
  end Write_Letter_A_To_Variable;

  task body Access_Variable is
    Letter : Character := Unprotected;
  begin
    loop
      Put (Letter);
      delay 3.0;
    end loop;
  end Access_Variable;

begin
  null;
end Unprotected_Shared_Variable;