QNX 4 had a function called tfork() that let you use “threads” by creating a process with its code and data segments mapped to the same memory locations as the creating process. This gave the illusion of a thread by creating a process, and then changing the characteristics of the newly created process to make it look like a thread. While there is a thread library available for QNX 4 on QNX Software Systems' update system, the kernel itself doesn't support threads directly.
Under QNX Neutrino, the POSIX “pthread” model is used for all threading. This means that you'll see (and have seen in this book) familiar function calls like pthread_create(), pthread_mutex_lock(), and others.