[j_s]

TL;DR (aka WTF?): The Design of an Operating System, a Compiler, and a Computer

a design for a complete computer system. Its simplicity and clarity enables a single person to know and implement the entire system

[timClicks]

Take a look at the Wikipedia entry if you would like an overview of the scale/scope of the project and its history: https://en.wikipedia.org/wiki/Oberon_%28operating_system%29