with Interfaces;    use Interfaces;
with Interfaces.C;  use Interfaces.C;
with System;        use System;

with Ada.Unchecked_Conversion;

procedure Hello is
   function LoadLibrary (lpFileName : char_array) return Unsigned_32;
   pragma Import (Stdcall, LoadLibrary, "LoadLibrary", "_LoadLibraryA@4");
 
   function GetProcAddress (hModule : Unsigned_32; lpProcName : char_array) return Address;
   pragma Import (Stdcall, GetProcAddress, "GetProcAddress", "_GetProcAddress@8");
   
   type MessageBox is access function (
      hWnd      : Address;
      lpText    : char_array;
      lpCaption : char_array;
      uType     : Unsigned_16
   ) return Integer_16;
   pragma Convention (Stdcall, MessageBox);

   function To_MessageBox is new Ada.Unchecked_Conversion (Address, MessageBox);
 
   Result : Integer_16;
   Library : Unsigned_32;
   Pointer : Address;
begin
   Library := LoadLibrary (To_C ("user32.dll"));
   Pointer := GetProcAddress (Library, To_C ("MessageBoxA"));
   Result := To_MessageBox (Pointer) (
      Null_Address,
      To_C ("Hello, Win32 API(Ada) World!"),
      To_C ("Hello, World!"),
      0
   );
end Hello;