In the days of mainframe computing, one system stood miles ahead of the rest. PLATO (Programmed Logic for Automatic Teaching Operations) wasn't special for its power or speed or graphical prowess, though. It was remarkable for the ideas that drove its development and for the breadth of its impact—starting in the 1960s and accelerating through the '70s and '80s, PLATO terminals became omnipresent throughout schools, universities, and offices around the world.
The PLATO system was designed for education. It had a programming language called TUTOR that was simple enough for non-technical people to use for writing software; it also notably offered a social environment. It was an online community as much as it was a computing platform, and in this capacity it envisaged much of the future of communication. PLATO had chat rooms, message boards, touch panels built into the (flat, plasma) screens, emoticons, animations, virtual economies, and more.