Keyboard and mouse cables and ports are almost invariably serial-such as PS/2 port, Apple Desktop Bus and USB.

The cables that carry this data (other than 'the' serial cable) and the computer ports they plug into are usually referred to with a more specific name, to reduce confusion. Practically all long-distance communication transmits data one bit at a time, rather than in parallel, because it reduces the cost of the cable. Many serial communication systems were originally designed to transfer data over relatively large distances through some sort of data cable.