Standard library header <iso646.h> (C95)
From cppreference.com
This header defines macros for alternative operator spellings.
Synopsis
#define and &&
#define and_eq &=
#define bitand &
#define bitor |
#define compl ~
#define not !
#define not_eq !=
#define or ||
#define or_eq |=
#define xor ^
#define xor_eq ^=
Notes
This header is meaningless in C++ because these macro names exist as keywords in C++ and are unconditionally available.