The typewriter started out as a system to produce legible, professional-quality one-off output by hand (as opposed to the typeset printing press). In this sense it was interface between human and paper, and also a middleman in the recording of thoughts, symbols, and characters. Additionally its typewritten output was further an interface between people--one's words represented unambiguously to another party minutes, days, or years later. As computers have grown in popularity, the interface has become more complex. Keyboards are now an interface between analog human thinking and digital computer operation, storage, and transmission. It's still a typewriter, but it outputs for the world instead of one person, and the audience has grown to include machines.