C++ Keywords must be in your knowledge because you can not use them as a variable name. This tutorial describes various Keywords available in C++.
You can't use a keyword as an identifier in your C++ programs; it's reserved words in the C++ library and used to perform an internal operation. The meaning and working of these keywords are already known to the C++ compiler.
C++ Keywords List
In addition, the following words are also reserved:
You should also try to avoid using names from the C++ library, e.g.