[Boost-users] identification of thread

Hi, Could you please explain for beginner in thread-related business, how the thread is identified from itself? Can the program, that it the given thread, obtain its own number or an index of itself? I assume that there should be some enumeration such as numbering the main program by 0, next child thread by 1, etc.? And, in particular, is this number available from boost thread library? THanks in advance Igor