Service Control Handler:
Whenever there is a change in the status of the service, this function gets called with the appropriate control code. This is also, where we can control the program's status.

The following program is a complete source code of a Win32 NT Service program.

To run this program,

1. In VC++, Create a new Win32 Console Application.
2. In the type of Application Wizard, choose "An Empty Project".
3. In the Menu, Project --> Add to Project --> New, Choose a C++ File.
4. Name the C++ file.
5. Copy the following source code.
6. Compile the application.
7. If you want to install the service, type the following in command prompt.
   "ProgramName.exe install"
   A message appears saying "CodeSourceService Installed Successfully".
8. If you want to remove it, type the following in command prompt. "ProgramName.exe remove"

#include <stdio.h>
#include <windows.h>
#include <tchar.h>

TCHAR* gszServiceName = TEXT("CoderSourceService");
SERVICE_STATUS serviceStatus;
SERVICE_STATUS_HANDLE serviceStatusHandle = 0;
HANDLE ServiceControlEvent = 0;
FILE *g_Handle; //Global File Handle
char gszFilePath[] = "C:\\SourceCoderServiceOutput.txt";


void WINAPI ServiceControlHandler( DWORD controlCode )
{
 switch ( controlCode )
  {
	case SERVICE_CONTROL_INTERROGATE:
	break;

	case SERVICE_CONTROL_SHUTDOWN:
	case SERVICE_CONTROL_STOP:
    	serviceStatus.dwCurrentState = SERVICE_STOP_PENDING;
		SetServiceStatus( serviceStatusHandle, &serviceStatus );

		SetEvent( ServiceControlEvent );
		return;

	case SERVICE_CONTROL_PAUSE:
		break;

	case SERVICE_CONTROL_CONTINUE:
		break;

	default:
		if ( controlCode >= 128 && controlCode <= 255 )
		// user defined control code
			break;
		else
		// unrecognised control code
			break;
	}

	SetServiceStatus( serviceStatusHandle, &serviceStatus );
}

void WINAPI ServiceMain( DWORD /*argc*/, TCHAR* /*argv*/[] )
{
	// initialise service status
	serviceStatus.dwServiceType = SERVICE_WIN32;
	serviceStatus.dwCurrentState = SERVICE_STOPPED;
	serviceStatus.dwControlsAccepted = 0;
	serviceStatus.dwWin32ExitCode = NO_ERROR;
	serviceStatus.dwServiceSpecificExitCode = NO_ERROR;
	serviceStatus.dwCheckPoint = 0;
	serviceStatus.dwWaitHint = 0;

	serviceStatusHandle = RegisterServiceCtrlHandler( gszServiceName,
	 ServiceControlHandler );

	if ( serviceStatusHandle )
	{
		// service is starting
	 serviceStatus.dwCurrentState = SERVICE_START_PENDING;
	 SetServiceStatus( serviceStatusHandle, &serviceStatus );

	// Create the Controlling Event here
 	 ServiceControlEvent = CreateEvent( 0, FALSE, FALSE, 0 );

	// Service running
	 serviceStatus.dwControlsAccepted |= (SERVICE_ACCEPT_STOP |
	 SERVICE_ACCEPT_SHUTDOWN);
	 serviceStatus.dwCurrentState = SERVICE_RUNNING;
	 SetServiceStatus( serviceStatusHandle, &serviceStatus );
	 fprintf(g_Handle,"CoderSource Service Created this file\n");
	 fflush(g_Handle);

	 WaitForSingleObject( ServiceControlEvent, INFINITE );

	// service was stopped
	 serviceStatus.dwCurrentState = SERVICE_STOP_PENDING;
	 SetServiceStatus( serviceStatusHandle, &serviceStatus );

	// do cleanup here
	 fclose(g_Handle);
	 CloseHandle( ServiceControlEvent );
	 ServiceControlEvent = 0;

	// service is now stopped
	 serviceStatus.dwControlsAccepted &= ~(SERVICE_ACCEPT_STOP |
		SERVICE_ACCEPT_SHUTDOWN);
	 serviceStatus.dwCurrentState = SERVICE_STOPPED;
	 SetServiceStatus( serviceStatusHandle, &serviceStatus );
	}
}

void RunService()
{
 SERVICE_TABLE_ENTRY serviceTable[] =
 {
 	{ gszServiceName, ServiceMain },
	{ 0, 0 }
 };

 StartServiceCtrlDispatcher( serviceTable );
}

void InstallService()
{
 SC_HANDLE serviceControlManager = OpenSCManager( 0, 0,
  SC_MANAGER_CREATE_SERVICE );

 if ( serviceControlManager )
 {
 	char path[ _MAX_PATH + 1 ];
	if ( GetModuleFileName( 0, path, sizeof(path)/sizeof(path[0]) ) > 0 )
	{
		SC_HANDLE service = CreateService( serviceControlManager,
			gszServiceName, gszServiceName,
			SERVICE_ALL_ACCESS, SERVICE_WIN32_OWN_PROCESS,
			SERVICE_AUTO_START, SERVICE_ERROR_IGNORE, path,
			0, 0, 0, 0, 0 );
    	if ( service )
		{
	      CloseServiceHandle( service );
		  printf("CoderSourceService Installed Successfully\n");
		}
		else
		{
		 if(GetLastError() == ERROR_SERVICE_EXISTS)
		   printf("CoderSourceService Already Exists.\n");
		 else
		   printf("CoderSourceService Was not Installed
		   Successfully. Error Code %d\n", GetLastError());
		}
	}

	CloseServiceHandle( serviceControlManager );
 }
}

void UninstallService()
{
 SC_HANDLE serviceControlManager = OpenSCManager( 0, 0,
 SC_MANAGER_CONNECT );

if ( serviceControlManager )
{
	SC_HANDLE service = OpenService( serviceControlManager,
		gszServiceName, SERVICE_QUERY_STATUS | DELETE );
	if ( service )
	{
		SERVICE_STATUS serviceStatus;
	if ( QueryServiceStatus( service, &serviceStatus ) )
	{
		if ( serviceStatus.dwCurrentState == SERVICE_STOPPED )
		{
			if(DeleteService( service ))
				printf("CoderSourceService Removed
				Successfully\n");
			else
			{
			DWORD dwError;
			dwError = GetLastError();
			if(dwError == ERROR_ACCESS_DENIED)
				printf("Access Denied While trying to Remove
				CoderSourceService \n");
			else if(dwError == ERROR_INVALID_HANDLE)
				printf("Handle invalid while trying to Remove
				CoderSourceService \n");
			else if(dwError == ERROR_SERVICE_MARKED_FOR_DELETE)
				printf("CoderSourceService already marked
				for deletion\n");
			}
		}
		else
		{
			printf("CoderSourceService is still Running.\n");
		}
		}
		CloseServiceHandle( service );
	}
	CloseServiceHandle( serviceControlManager );
	}
}

int _tmain( int argc, TCHAR* argv[] )
{
	if ( argc > 1 && lstrcmpi( argv[1], TEXT("install") ) == 0 )
	{
		InstallService();
	}
	else if ( argc > 1 && lstrcmpi( argv[1], TEXT("remove") ) == 0 )
	{
		UninstallService();
	}
	else
	{
		if((g_Handle = fopen(gszFilePath, "w")) != NULL)
			RunService();
		else
			exit(1);
	}
	return 0;
}