A digital universe – whether 5 kilobytes or the entire internet – consists of two species of bits: differences in space and differences in time. Digital computers translate between these two forms of information – structure and sequence – according to definite rules. Bits that are embodied as structure (varying in space, invariant across time) we perceive as memory, and bits that are embodied as sequence (varying in time, invariant across space) we perceive as code. Gates are the intersections where bits span both worlds at the moments of transition from one instant to the next.
George Dyson, Turing’s Cathedral.