Operating system application programmer interfaces (API) and their role in open systems for avionics

Operating System (OS) application programmer interfaces (APIs) are a key enabler to target independent software and seamless upgrading from the software perspective when the underlying hardware is changed. This is one of the significant cost reduction mechanisms promised by the use of open systems. This paper discusses on-going work within IEEE Portable Operating Systems Interfaces (POSIX) and SAE AS5B2 Operating System API working group that address providing a suitable OS API for real-time avionic systems. This paper also describes how the OS API is a significant part of the target independent software story and how it fits in with the generic open avionics architecture model being developed by the SAE. The POSIX discussions summarize what has been going on in POSIX, with particular attention to the real-time working groups. Most attention is given to activities occurring in P1003.21 Real-Time Distributed Systems Communications.