This standard is part of the POSIX series of standards for applications and user interfaces to open systems. It defines the applications interface to basic system services for input/output, file system access, and process management. It also defines a format for data interchange. When options specified in the Realtime Extension are included, the standard also defines interfaces appropriate for realtime applications. When options specified in the Threads Extension are included, the standard also defines interfaces appropriate for multithreaded applications. This standard is stated in terms of its C language binding.