I'm assuming the answer to b) is consistent standards (applied to all Google engineers). However, the answer to c) is what I want to know, because it relates to how Thompson currently works. Does anybody have more information on this?
It's not really a programming "test", it's a special code review where you submit a block of code you've written that's already part of a production system, and then a reviewer goes over it with a fine-toothed comb for style violations, knowledge of the language fundamentals, proper usage of typical library functions, and good testing practice. While it is possible to "fail" a readability review, that usually only happens if you completely do not understand the basics of the language. Usually the reviewer will work with you to improve the code until it's suitable.
It's also not unheard of for code written during these readability reviews to become useful production code. For example, my JS readability reviewer asked me to write a quick mock-object framework, to prove that I understood how classes, objects, and prototypes worked since the code I had submitted used none of these. This was later pulled out into its own library, at the request of some coworkers, and now is used for testing a bunch of websearch JavaScript.
You've guessed b.) correctly.
As for c.), you can still check in code without having readability, you just need to find someone with readability to review and approve it. I think it's a fairly good bet that Ken Thompson works with someone with C++ readability, and since all code needs to be reviewed anyway, it basically doesn't matter.
It actually fairly common for engineers to not bother getting readability, both because they can count on others to review their code and because the readability process requires that you submit a large chunk of code that was "primarily authored" by yourself. That latter bit disqualifies most code, because most Googlers work on teams and we end up rewriting our code several times before it's stable. I submit C++ all the time, but I still don't have C++ readability, because most of my changes have been edits (sometimes fairly extensive) to a class that somebody else wrote.
http://www.reddit.com/r/programming/comments/bu6j1/c_languag...
The Register is good at clever headlines that are not really lies - and often with decent content. In this case, they notoriously failed at both. The comments usually have some well informed posters, too, if you feel like digging.
(And for occasional humor and wit, I like http://www.theregister.co.uk/odds/bofh/ and http://www.theregister.co.uk/odds/stob/ )