a Being in a state of one of two mutually exclusive conditions such as on or off, true or false, presence or absence of a signal.
a (mathematics|programming|computer engineering) Of an operation, function, procedure(,) or logic gate, taking exactly one operand, argument, parameter(,) or input; having domain of dimension 2.
a (computing) Of data, consisting of arbitrary values; that is, not interpretable as plain or ASCII text.
n (mathematics|computing|uncountable) The bijective base-2 numeral system, which uses only the digits 0 and 1.