Oberon System

Wirth came back from a sabbatical at Xerox PARC in 1985 with impressions of Cedar and the conviction that most things could be made smaller. With Gutknecht he built the Oberon language, the Ceres workstation and an operating system for it, all as one project. The screen is split into two vertical tracks, one for the user's texts and one for the system's, and inside each track "viewers" are stacked without overlapping: a tiled interface a decade before the term. No icons, no menus. Commands are text: if Edit.Open appears anywhere on screen, a middle click on the word runs that procedure, and a viewer's title bar is simply a line of such words.

The whole system, compiler, editor and window system included, was described in the 1992 book Project Oberon and fit in a few thousand lines. Rob Pike has cited Oberon as a model for acme in Plan 9, which borrowed both the tiling and the idea that executable text is the only interface you need. Oberon System 3 added components called Gadgets, and Bluebottle, later A2, brought overlapping windows and multiprocessor support. In 2013 Wirth rewrote the book around his own RISC processor on an FPGA, so the system could once again run on hardware with nothing underneath it.