The HP DCE package (version 1.5) shipped with HP-UX 10.x provides support
for a threads package derived from The Open Group[TM]'s DCE 1.2.1 version
which is based on the POSIX.4a draft 4 API and several extensions. In
addition, it provides an exception support not specified in the POSIX.4a.
HP-UX 10.x DCE threads are user-space threads.

For more information on DCE threads, see thr_intro(3).

HP-UX 11.x ships with DCE v1.7.  In addition, 11.x provides a POSIX
threads package based on the POSIX.1c-1996 standard.  11.x POSIX threads
are kernel-space threads.

For more information on POSIX.1c threads, see pthread(3T).

For an in-depth look at threads, pick up a copy of the book:

  "ThreadTime" by Scott J. Norton and Mark D. DiPasquale, Prentice-Hall,
  ISBN 0131900676, 1996.

Another valuable resource is the comp.programming.threads FAQ:

  o <http://www.serpentine.com/blog/threads-faq/>