WITH Ada.Text_IO;
WITH Screen;
PROCEDURE Columns IS
------------------------------------------------------------------
--| Shows tasks writing into their respective columns on the
--| screen. This will not always work correctly, because if the
--| tasks are time-sliced, one task may lose the CPU before 
--| sending its entire "message" to the screen. This may result
--| in strange "garbage" on the screen.
--| Author: Michael B. Feldman, The George Washington University 
--| Last Modified: December 1995                                     
------------------------------------------------------------------

  TASK TYPE SimpleTask (Message: Character; 
                        HowMany: Screen.Height;
                        Column:  Screen.Width) IS

    -- This specification provides a "start button" entry.
    ENTRY StartRunning;

  END SimpleTask;

  TASK BODY SimpleTask IS

  BEGIN -- SimpleTask
    
    -- Each task will write its message in its own column
    ACCEPT StartRunning;

    FOR Count IN 1..HowMany LOOP
      Screen.MoveCursor(To=>(Row => Count, Column => Column));
      Ada.Text_IO.Put(Item => "Hello from Task " & Message);
      DELAY 0.5;            -- lets another task have the CPU
    END LOOP;

  END SimpleTask;

  -- Now we declare three variables of the type
  Task_A: SimpleTask(Message => 'A', HowMany => 5, Column => 1);
  Task_B: SimpleTask(Message => 'B', HowMany => 7, Column => 26);
  Task_C: SimpleTask(Message => 'C', HowMany => 4, Column => 51);

BEGIN -- Columns
  
  Screen.ClearScreen;
  Task_B.StartRunning;
  Task_A.StartRunning;
  Task_C.StartRunning;

END Columns;