Standard library header <iso646.h> (C95)
From cppreference.net
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.