subtype Valid_X is Positive range 1 .. 20;
   subtype Valid_Y is Positive range 1 .. 15;

   No_Of_Squares_X : constant Valid_X := 20;
   No_Of_Squares_Y : constant Valid_Y := 15;

   type Arr_Column is
     array (0 .. No_Of_Squares_Y+1) of Character;

   type Board_Type is
     array (0 .. No_Of_Squares_X+1) of Arr_Column;