The Paper Computer Unfolded

Book excerpt: "The Paper Computer Unfolded" reveals the untold true story of three fully programmable computers that were made of nothing more than paper, cardboard, a bit of glue, and a lot of imagination.From transistors to lasers, from radio astronomy to the solar battery cell, and from the C programming language to information theory, through much of the twentieth century Bell Telephone Laboratories was the birthplace of the future. But just as important as what the scientists and mathematicians at Bell Labs invented were their clever promotional efforts describing the nature of their work. For instance, in the 1960s Bell distributed self-promotional "advertisements" in the form of free scientific and technology kits to teachers and students in middle and high schools nationwide. One kit focused on transistors; another, on solar energy; and yet another, on crystals and light. By the end of the sixties, many high school students received their first exposure to computers courtesy of the "Understanding Computers" Bell Labs kit. Inside was a strange-looking device constructed out of paper and die-cut cardboard: the CARDboard Illustrative Aid to Computation (CARDIAC), a fully programmable computer created by a visionary Bell mathematician. The single-address, single-accumulator-based CARDIAC needed (rather fittingly) just a single power source to run programs on its hardware: you. Hand-operated, no electricity required. With the relative scarcity of electronic computers and the expense of computer time, there was perhaps no better teaching tool than the CARDIAC.The story of the paper computer, however, doesn't end with the CARDIAC; in fact, it probably doesn't even begin with it. Several years before Bell Labs released their "Understanding Computers" kit, a young Massachusetts Institute of Technology doctoral student developed his own instructional model: the Little Man Computer (LMC). With a design and instruction set quite similar to the CARDIAC, the LMC--requiring nothing more than paper and pencil to run programs--quickly caught on at MIT, where it was taught to all undergraduates studying computers. Decades later, the LMC paradigm, in various incarnations, still persists in computer science curricula around the country.And improbably, despite the ascension and growing availability of cheap microcomputers by the late 1970s, a third paper computer, called the Instructo, was patented and released. If the CARDIAC was a product of the research lab and the LMC a product of the ivory tower, the Instructo was a true product of the classroom: it was developed by a prolific mathematics teacher who knew a thing or two about teaching computers to middle and high school students. Vastly different from the other two machines, the Instructo Paper Computer (IPC) has a large instruction set and multiple registers and switches "powering" its cardboard components. But like the CARDIAC and the LMC, the IPC models a von Neumann architecture, albeit also without the need for an electric power source.Tracing their origins to the early calculating machines of Pascal and Babbage, through the groundbreaking computational theories of Turing and von Neumann, to the first electromechanical and electronic computers, and finally to the influence of other instructional models like the TUTorial Automatic Computer (TUTAC) and the infamous paperclip computer, "The Paper Computer Unfolded" is the most thoroughly researched book available on the design and development of the CARDIAC, the LMC, and the IPC. Mark Jones Lorenzo's eminently readable book, which fuses the technical jargon of a computer manual with the prose of a true page-turner, also contains many example paper computer programs written in both machine and assembly language, code listings of emulators for all three machines, as well as cartoon illustrations paying homage to the innovative CARDIAC manual.