The POSIX 1003.1-2001 standard defines an application programming interface (API) for writing multithreaded applications. This interface is known more commonly as pthreads. A good number of modern operating systems include a threading library of some kind: Solaris (UI) threads, Win32 threads, DCE threads, DECthreads, or any of the draft revisions of the pthreads standard. The trend is that most of these systems are slowly adopting the pthreads standard API, with application developers following suit to reduce porting woes.