thanks Pert, that looks like a useful, Bookmarked.
@ J-M-L, yes , as always it's case of getting the right words. I was thinking "C language" rather than c++ and probably stuck on "define" rather than your more generic term and I was thinking compiler directives not preprocessor directives.
Searching for C does not work because G just ignores it. You then get left with "language" which is a total red herring.
As I suspected , it's just a case of not getting the right words in there.