But [Ken] Thompson and the others helping him knew that the PDP‑7, which was already obsolete, would not be able to sustain their skunkworks for long. They also knew that the lab's management wasn't about to allow any more research on operating systems.
So Thompson and [Dennis] Ritchie got creative. They formulated a proposal to their bosses to buy one of DEC's newer minicomputers, a PDP-11, but couched the request in especially palatable terms. They said they were aiming to create tools for editing and formatting text, what you might call a word-processing system today. The fact that they would also have to write an operating system for the new machine to support the editor and text formatter was almost a footnote.
07 December 2011
Nice recap by Warren Toomey of the genesis of the ultimate under-the-radar project, Unix.