C Language Reference, and identifier lengths (follow-up)

Followup to: https://software.intel.com/en-us/forums/intel-c-compiler/topic/736065

This question was answered by providing a link to the compiler reference, thanks.

But actually, I am looking for a language reference, not a compiler reference, and I originally posted because I haven't been able to find a language reference in the compiler reference. Nor have I been able to find the identifier length limits.

Thanks,
Kevin