When a thread is created, a new thread of control is added to the current process. Every process has at least one thread of control, in the program's main() routine. Each thread in the process runs simultaneously, and has access to the calling process's global data. In addition each thread has its own private attributes and call stack.
To create a new thread, a running thread calls the pthread_create() function, and passes a pointer to a function for the new thread to run. One argument for the new thread's function can also be passed, along with thread attributes. The execution of a thread begins with the successful return from the pthread_create() function. The thread ends when the function that was called with the thread completes normally.
A thread can also be terminated if the thread calls a pthread_exit() routine, or if any other thread calls pthread_cancel() to explicitly terminate that thread. A thread can also be terminated by the exit of the process that called the thread.