Windows implements the same program that runs without running a new program.

It is mainly through mutex kernel objects to achieve inter-program mutual exclusion.

Cecopclientapp initialization
HANDLE M_hmutexmark = NULL;
BOOL cecopclientapp::initinstance ()
{
Program mutex code to ensure that only one copy of the program is running---------------
M_hmutexmark =:: CreateMutex (NULL, TRUE, "Myecopclient_mark");
if (GetLastError () = = error_already_exists)//program already running
{
HWND Oldhwnd = NULL;
Oldhwnd =:: FindWindow (NULL, _t (dfsystemname)); Find a program that is already running

if (Oldhwnd)
{
:: ShowWindow (Oldhwnd, sw_maximize); Activate show found running program
:: SetForegroundWindow (Oldhwnd); To set a running program as the current window
}
CloseHandle (M_hmutexmark);
M_hmutexmark = NULL;
return FALSE;
}

Windows implements the same program that runs without running a new program.