7 Expressions [expr]

7.6 Compound expressions [expr.compound]

7.6.11 Bitwise AND operator [expr.bit.and]

and-expression & equality-expression
The & operator groups left-to-right.
The operands shall be of integral or unscoped enumeration type.
The usual arithmetic conversions ([expr.arith.conv]) are performed.
Given the coefficients and of the base-2 representation ([basic.fundamental]) of the converted operands x and y, the coefficient of the base-2 representation of the result r is 1 if both and are 1, and 0 otherwise.
The result is the bitwise AND function of the operands.
— end note