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Traf-O-Data is a story from the Forces of Change section of the STARTUP Gallery. Click on the map to explore any section of the gallery.

The Traf-O-Data was a computerized machine for processing paper tapes from traffic counters, those black hoses most of us have driven over on roads throughout the United States. It was an early example of a microprocessor-controlled “embedded system,” not really a computer as we know it, but computerized, the way microwave ovens and DVD players and just about everything else is computerized today. As a product it failed, and would have disappeared from history without a ripple were not two of the people involved named Paul Allen and Bill Gates.

This was not the first business venture for Gates and Allen. Their Lakeside Programming Group, formed a year or two earlier, in 1970, had been involved in some impressive software projects by then, most recently at TRW working on software to control the Northwest power grid. Traf-O-Data was a little different. It began with the idea of automating the processing of traffic tapes for the local road department, which a group of students at Gates’s and Allen’s Lakeside School was doing by hand at the time. This would be another software project, but it would also require special hardware—a computer of some sort. They ruled out minicomputers because they were too expensive. Intel’s 8008 chip had just come out, and they decided to use it to build their own special-purpose computer.

Neither had much hardware experience, so they enlisted the help of a friend, Paul Gilbert, to construct the machine while they wrote the software. There they ran into another problem: how do you program a machine that doesn’t exist yet? They used a technique Allen had become interested in called computer emulation.

Emulation was a pretty exotic concept in 1972, especially for a kid barely out of high school. The term had first been applied to computers some eight years earlier by IBM engineer Larry Moss, who used a sophisticated technique called microprogramming to allow the new IBM System/360 computers to run software written for earlier IBM computers. The 360, in other words, would emulate the earlier computer. He preferred the word “emulation” to “simulation” to emphasize the fact that the 360 machines would run the programs even faster than the original machines. Since then, attempts to mimic the behavior of another machine have been called “emulation” whether written in microcode or in a higher-level language.

Writing in assembly language, Allen programmed a PDP-10 to emulate the Intel 8008 microchip, and he and Gates were able to complete the Traf-O-Data software before the machine was even operational.

The plan was to manufacture the Traf-O-Data and sell it to state and local governments, but their one demo was a failure. The tape reader malfunctioned and the sale was lost. They repaired and debugged the machine, but it never became a product—which was fortunate. Success would have distracted Gates and Allen at a crucial moment. As it was, by the time the lone Traf-O-Data began processing traffic tapes in 1975, the two had turned the operation over to Gilbert and moved on to form Microsoft.

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