<ciso646>
Includes the C standard library header <iso646.h>, and adds the associated names to the std namespace.
Note
Because this compatibility header defines names that are keywords in C++, including it has no effect. The <iso646.h> header is deprecated in C++. The <ciso646> header is removed in the draft C++20 standard.
Requirements
Header: <ciso646>
Namespace: std
Remarks
Including this header ensures that the names declared using external linkage in the C standard library header are declared in the std namespace.
See also
Header files reference
C++ standard library overview
Thread safety in the C++ standard library