It seems obvious now: People are the “killer app” for computers. Computers are less about computing and much more about communication, connection and community. Facebook, LinkedIn, YouTube, email, instant messaging, multiplayer games and discussion forums—today’s most popular uses of computers are all about human interaction.

It wasn’t always so, nor was it always so obvious. In “The Friendly Orange Glow,” author and technology entrepreneur Brian Dear tells the fascinating story of Plato, an educational computer system developed during the 1960s and 1970s that was used by tens of thousands of students. Plato astonishes in multiple ways. Technologically, it was far ahead of its time, offering its users the flat-panel graphical displays, touch screens and collaborative apps we take for granted today. Socially, its users formed some of the earliest online communities, dozens of years before they would become commonplace. Historically, it is virtually unknown; it is as if, Mr. Dear writes, “an advanced civilization had once thrived on earth, dwelled among us, built a wondrous technology, but then disappeared as quietly as they had arrived.”

Mr. Dear traces Plato’s origins to the 1950s, starting with the psychologist B.F. Skinner’s quest for an “automatic teacher” that would allow students to pace themselves and receive instant feedback—a quest that picked up steam with the 1957 launch of the Soviet Sputnik satellite and the ensuing U.S. “educational emergency.” People soon realized that this newfangled thing called a “computer” might be the perfect teacher: While expensive, it might, with the right programming and remote terminals, provide teaching precisely tuned to students’ needs.

Plato—Programmed Logic for Automatic Teaching Operations—began its life in 1960 at the University of Illinois’s Control Systems Laboratory, a defense lab run by physicists and engineers. Plato’s fathers were the lab’s director, Daniel Alpert, and the project lead, freshly minted Ph.D. Don Bitzer. Mr. Dear likens them respectively to a “venture capitalist” and a “whiz-kid start-up founder.”

Over the next two decades Mr. Bitzer led a crew through numerous challenges. How would they build a system capable of supporting multiple users? How would instructors create lessons without having to become expert computer programmers? How would the remote computer terminals work? How could they be made cost-effectively? Their novel solution to this last problem gives the book its title: The Plato team developed the flat-panel plasma display—which at the time could only produce one color. As a result, Plato terminals bathed their users in a distinctive orange light that users came to call the “Friendly Orange Glow.”