Operating System Design/Case Studies/BeOS
BeOS is an operating system for personal computers. It was under development from 1991 until development was discontinued in 1997. Although it has partial compatibility with POSIX and a Bash shell, it is not based on Unix sources and remains closed-source.
The open-source Haiku operating system aims to pick up where BeOS left off. It began development in 2001 and became self-hosting and 2008.