PLATO (Programmed Logic for Automated Teaching Operations) was the first (ca. 1960, on ILLIAC I) generalized computer assisted instruction system, and, by the late 1970s, comprised several thousand terminals worldwide on nearly a dozen different networked mainframe computers. Originally, PLATO was built by the University of Illinois and functioned for four decades, offering coursework (elementary–university) to UIUC students, local schools, and other universities. Several descendant systems still operate.
The PLATO project was assumed by the Control Data Corporation (CDC), who built the machines with which PLATO operated at the University. CDC President William Norris planned to make PLATO a force in the computer world; the last production PLATO system was shut down in 2006 (coincidentally, just a month after Norris died), yet it established key on-line concepts: forums, message boards, online testing, e-mail, chat rooms, picture languages, instant messaging, remote screen sharing, and multi-player games.
In 1960, the first system, PLATO I, operated on the local ILLIAC I computer. It included a television set for display and a special keyboard for navigating the system's function menus; PLATO II, in 1961, featured two users at once. PLATO III allowed "anyone" to design new lesson modules using their TUTOR programming language, conceived in 1967. PLATO III could simultaneously run up to 20 lessons, and was used by a local facilities in Champaign-Urbana that could enter the system with their custom terminals. In 1972 a new system named PLATO IV was ready for operation. The PLATO IV terminal was a major innovation. It included Bitzer's orange plasma display invention which incorporated both memory and bitmapped graphics into one display. This plasma display included fast vector line drawing capability and ran at 1260 baud, rendering 60 lines or 180 characters per second. The display was a 512x512 bitmap, with both character and vector plotting done by hardwired logic. Users could provide their own characters to support rudimentary bitmap graphics. Compressed air powered a piston-driven microfiche image selector that permitted colored images to be projected on the back of the screen under program control. The PLATO IV display also included a 16-by-16 grid infrared touch panel allowing students to answer questions by touching anywhere on the screen.
Source: Wikipedia, "PLATO (computer system)," available under the CC-BY-SA License.