problem in threading c++ -

i running 2 threads , text display first displayed after execution of thread

string thread(string url) {     mutex.lock();     //some function goes here      mutex.unlock(); }  int main() {     cout<<"asd";      boost::thread t1(boost::bind(&thread));      boost::thread t2(boost::bind(&thread));      t1.join();     t2.join(); } 

in main program have displayed text asd displayed after execution of thread ..

std::cout << "asd" << std::flush;