All operating systems (OSs) in this category support POSIX standards fully or partly. POSIX is an acronym for: Portable Operating System Interface for UniX. Much like TRON, POSIX is not a body of computer code that is compiled and run on some processor. Rather, it is a set of standards (IEEE 1003.1): interfaces, design guidelines, software design specifications, defining (for creating) the computer code that will become language interfaces between an OS kernel and its programs, to give compatibility when moving programs between compatible systems. POSIX is made mostly of features from BSD Unix and Unix System V. Much like Open Source software, all POSIX standards are copyrighted (by the Institute of Electrical and Electronics Engineers, Inc., IEEE; new versions have joint copyright by IEEE and Open Group), but available for use by software developers anywhere in the world for free. Thus the OS architecture based on POSIX is an open architecture that invites and welcomes cloning and interoperability. On this page, OSs are arranged in two groups and levels: 1) Top group: types or classes of OS. 2) Bottom group: specific OSs, individual instances; there is only one OS of this name/type.
Secure, no royalty, for high reliability embedded systems; hardware memory protection to isolate and protect it and user tasks from incorrect operation by errors or tampering; object-oriented design allows verifying data security/integrity, communications, individual components, whole system; strict adherence to provable resource requirements. Green Hills Software, Inc.
Growing article, with links to many related topics. Wikipedia.
Realtime kernel for embedded uses, follows Minimal Real-Time POSIX.13 subset. Most code is Ada, but some C, assembly. Hardware access via Abstract Hardware Interface (HAL). Runs in cross development environment: PC Linux Host, bare 386 PC Target, Ethernet LAN link. [Open Source, GPL]
Dynamic configurable kernel architecture to support hard/soft/non realtime use with interchangeable scheduling algorithms: fully modular in scheduling policies, aperiodic servers, concurrency control protocols; all not modular in most traditional OSs. Derived from HARTIK: HArd Real TIme Kernel. [Open Source, GPL]
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