I feel I should point this out because it seems to be a point of confusion: "PDP" is not a single unified product line. The numbers do not indicate linear progress. There is no architectural relationship between a PDP-8, a PDP-10, and a PDP-11. "PDP" is just the TLA for "Programmed Data Processor", the term DEC used instead of "Computer" to avoid the business/political connotations that the word "computer" had at the time.
Allegedly the term was used so DEC equipment was classified as lab equipment and went through a different procurement process so it didn't end up in the typical computer center glassed off by IT gatekeepers and bureaucracy.
