I have seen many sentences/words in quotes like ``this'' instead of "this". Here's one from K&R:
In 1983, the American National Standards Institute (ANSI) established a committee whose goal was to produce ``an unambiguous and machine-independent definition of the language C'', while still retaining its spirit.
I have seen this especially more in text written about programming but in parts it means nothing special from a programming point of view.
I assume it is meant to differentiate string literals from quotations but I couldn't find anything related on the Internet and it is really hard to search about this since Google ignores most forms of punctuation.
My question: Exactly why is this done?