Detect Windows x32-x64 example

program bitness;

{$mode objfpc}{$H+}
{$APPTYPE CONSOLE}
uses {$IFDEF UNIX} {$IFDEF UseCThreads}
  cthreads, {$ENDIF} {$ENDIF}
  Classes,
  SysUtils,
  Windows;

  function IsWindows64: boolean;
  {
  Detect if we are running on 64 bit Windows or 32 bit Windows,
  independently of bitness of this program.
  Original source:
  http://www.delphipraxis.net/118485-ermitteln-ob-32-bit-oder-64-bit-betriebssystem.html
  modified for FreePascal in German Lazarus forum:
  http://www.lazarusforum.de/viewtopic.php?f=55&t=5287
  }
{$ifdef WIN32} //Modified KpjComp for 64bit compile mode
  type
    TIsWow64Process = function( // Type of IsWow64Process API fn
        Handle: Windows.THandle; var Res: Windows.BOOL): Windows.BOOL; stdcall;
  var
    IsWow64Result: Windows.BOOL; // Result from IsWow64Process
    IsWow64Process: TIsWow64Process; // IsWow64Process fn reference
  begin
    // Try to load required function from kernel32
    IsWow64Process := TIsWow64Process(Windows.GetProcAddress(
      Windows.GetModuleHandle('kernel32'), 'IsWow64Process'));
    if Assigned(IsWow64Process) then
    begin
      // Function is implemented: call it
      if not IsWow64Process(Windows.GetCurrentProcess, IsWow64Result) then
        raise SysUtils.Exception.Create('IsWindows64: bad process handle');
      // Return result of function
      Result := IsWow64Result;
    end
    else
      // Function not implemented: can't be running on Wow64
      Result := False;
{$else} //if were running 64bit code, OS must be 64bit :)
  begin
   Result := True;
{$endif}
  end;

begin
  try
    if IsWindows64 then
    begin
      writeln('This operating system is 64 bit.');
    end
    else
    begin
      writeln('This operating system is 32 bit.');
    end;
  except
    on E: exception do
    begin
      writeln('Could not determine bitness of operating system. Error details: ' + E.ClassName+'/'+E.Message);
    end;
  end;
end.