with Ada.Text_IO;
procedure ArrayTest is
type Index_Type is new Positive;
package Index_IO is new Ada.Text_IO.Integer_IO (Index_Type);
type Element_Type is new Natural;
type My_Array_Type is array (Index_Type range <>) of Element_Type;
type My_Array_Access is access My_Array_Type;
My_Index : Index_Type;
My_Array : My_Array_Access;
begin
Ada.Text_IO.Put ("Please enter maximum Index: ");
Index_IO.Get (My_Index);
My_Array := new My_Array_Type (1..My_Index);
-- work with My_Array...
end ArrayTest;