From Lazarus-ccr

unit opersys_u;

{$mode objfpc}{$H+}

interface

uses

 Classes, SysUtils, LResources, Forms, Controls, Graphics, Dialogs, StdCtrls;

type

 { TForm1 }

 TForm1 = class(TForm)
   Button1: TButton;
   procedure Button1Click(Sender: TObject);
   procedure FormCreate(Sender: TObject);
 private
   { private declarations }
 public
   { public declarations }
 end; 

var

 Form1: TForm1; 

implementation var

 os:byte;

{ TForm1 }

procedure TForm1.FormCreate(Sender: TObject); begin

 os:=0;
 {$IFDEF WIN32} // bezi WINDOWS
   os:=1;
 {$ENDIF}
 {$IFDEF LINUX} // bezi linux
   os:=2;
 {$ENDIF}

end;

procedure TForm1.Button1Click(Sender: TObject); var

 s:string;

begin

 s:='Spuštěn operační systém ';
 case os of
   0 : messagedlg(s+'neznámý', mtwarning,[mbok],0);
   1 : messagedlg(s+'WINDOWS', mtwarning,[mbok],0);
   2 : messagedlg(s+'LINUX', mtwarning,[mbok],0);
 end;

end;

initialization

 {$I opersys_u.lrs}

end.