FindCmdLineSwitch('service', ['-', '\', '/'], True)

procedure MainProc(ArgCount: DWORD; var Args: array of PChar); stdcall;
var
  Context: DWORD;
begin
 Context := Context;
 StatusHandle := RegisterServiceCtrlHandlerEx(Name, @ServicesCtrlHandler, @Context);
 if (StatusHandle <> 0) and Initialize and NotifyIsRunning then
//    while Status.dwCurrentState <> SERVICE_STOP do
     try
        // Собственно работа сервиса
//         Sleep(10);
     except
          // Обработка ошибок сервиса
     end;
 ExitThread(0);
end;

type

 TMyService = class (THybridApplication)
 private
   FServiceMonitor: TServiceMonitorThread;
 public
   procedure Init; override;
   procedure Done; override;
   function GetServiceController: TServiceController; override;
   function GetServiceMainProc: TServiceMainProc; override;
 end;

var
 MyApp: TMyService;

implementation

//------------------------------------------------------------------------------

procedure ServiceController(CtrlCode: DWord); stdcall;
begin
 MyApp.Controller(CtrlCode);
end;

//------------------------------------------------------------------------------

procedure ServiceMainProc(ArgCount: DWORD; var Args: array of PChar); stdcall;
begin
 MyApp.MainProc(ArgCount, Args);
end;

//------------------------------------------------------------------------------

function TMyService.GetServiceController: TServiceController;
begin
 Result := ServiceController;
end;

//------------------------------------------------------------------------------

function TMyService.GetServiceMainProc: TServiceMainProc;
begin
 Result := ServiceMainProc;
end;

//------------------------------------------------------------------------------

procedure TMyService.Init;
begin
 StartLog;
 try
   // тут стартуем все потоки выполняющие полезную работу
 except
   on e: Exception do
     Logger.Error(e.ClassName + ' : ' + e.Message);
 end;
end;

//------------------------------------------------------------------------------

procedure TMyService.Done;
begin
 try
   // тут останавливаем все потоки выполняющие полезную работу
 except
   on e: Exception do
     Logger.Error(e.ClassName + ' : ' + e.Message);
 end;
 StopLog;
end;

 MyApp := TMyService.Create(rsServiceName,
                                            rsServiceDisplayName,
                                            rsServiceDesc);
 try
   MyApp .Run;
 finally
   MyApp .Free;
 end;

program myprog;

{$APPTYPE CONSOLE}

uses
 SysUtils,
 SvcMgr,
 SvcUnit in 'SvcUnit.pas' {Service1: TService},
 Console in 'Console.pas';

{$R *.RES}

begin
 if FindCmdLineSwitch('service', ['-'], True) then
   begin
     if not Application.DelayInitialize or Application.Installing then
       Application.Initialize;
     Application.CreateForm(TListener, Listener);
     Application.Run;
   end
 else
     begin
       Work('MYPROG');
     end;
end.

unit Console;

interface

uses
   SysUtils;

procedure Work(const Invit: String);

implementation

procedure Work(const Invit: String);
var
  Terminated: Boolean;
  Input: String;
begin
 Terminated := False;
 while not Terminated do
   begin
     Write(Invit + '> ');
     ReadLn(Input);
     if ANSILowerCase(Input) = 'exit' then
       Terminated := True;
   end;
end;

end.

program myprog;

uses
 Windows;

begin
  WriteLn('Test');
  ReadLn;
end.

project myprog.exe raised exception class EInOutError with message 'I/O error 105'.