Is stdlib.h and cstdlib are same or different and how?

Question

Or they have different compiler??

Answer 1

They are the same, its just that cstdlib is the standard version, renamed like this after the standardization of the headers.

The new standardized c++ headers (which were now binded to the standard namespace) were differentiated from the old ones by the omitted '.h' from their names. The headers imported from C had a 'c' added before their names after the '.h' was omitted.