conditional compilation statement in limits.h

Question

I am not able to understand the following statement from the file limits.h. What is the use of this statement and what does it accomplishes?

/* If we are not using GNU CC we have to define all the symbols ourself.
   Otherwise use gcc's definitions (see below).  */
#if !defined __GNUC__ || __GNUC__ < 2

Answer 1

It checks if your program is compiled by some other compiler than GCC, or some very old GCC version.

Answer 2

It checks whether you are not using a Gcc compiler Version 2 or Gcc some other versions. using this pre-processor macro we can some portable codes.