pthread_create에서 궁금한 점이 있습니다.

int main()
{
    TestStart();
 
    return 0;
}
로
void *MyThread(void *data)
{
    printf("thread call\n");
    int i;
    int a = *(int *)data;
 
    printf("data = %d\n", a);
}
 
 
void TestStart(void)
{
    int a = 100;
    pthread_t thread_t;
    int status;
 
    pthread_create(&thread_t, NULL, MyThread, (void *)&a);
    //usleep(100);
 
    //printf("join start\n");
    //pthread_join(thread_t, (void **)&status);
    //printf("join end\n");
}