Niklaus Wirth, Jürg Gutknecht and ETH Zurich, 2003. Independent.
The Oberon System is a modular, single-user operating system written in the Oberon programming language. Niklaus Wirth and Jürg Gutknecht designed and implemented it at ETH Zurich in the late 1980s, as part of the Ceres workstation project, and documented it fully in their book Project Oberon.
Its text user interface is neither a command line nor a conventional graphical interface. Text almost anywhere on the screen can be edited and used as a command: a middle-click on a word of the form Module.Command runs that command. The design influenced the Acme text editor of Plan 9 from Bell Labs.
A team at ETH Zurich later extended Oberon and ported it to other hardware. Native Oberon runs on bare hardware, and its basic system fits on one high-density floppy disk. This exhibit runs PC Native Oberon dated 5 January 2003, the latest Native Oberon before its successors became AOS, Bluebottle and A2. In 2013, a few months before his 80th birthday, Wirth published a new edition of Project Oberon for a RISC processor of his own design.