The logical extreme would be to have only one data wire, which is often done. If there is only one data wire, we say that we have a serial bus since all the data bits flow in a serial or sequential fashion in time, one after another. The contrasting scheme, where there are many data wires and they all transmit a part of the value at the same time, is called a parallel bus because the data values are traveling together in parallel over the wires from their source to their destination.