Legacy Code

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By Martin English | November 19, 2007

America’s original electric grid, built by Thomas Edison in Manhattan in 1882 and soon replicated in many other cities, was a direct current system. But the DC grid was doomed by its inefficiency, and proved shortlived. When it became feasible to send power as alternating current, the new AC system quickly displaced the DC system.

But traces of the old DC system remain. In fact, as this NY Times story reports, it was only last week, November 15 2007, - 125 years after Edison constructed his original grid - that New York City’s electric utility, Con Edison, is finally shutting it down:

The last snip of Con Ed�s direct current system will take place at 10 East 40th Street, near the Mid-Manhattan Library. That building, like the thousands of other direct current users that have been transitioned over the last several years, now has a converter installed on the premises that can take alternating electricity from the Con Ed power grid and adapt it on premises. Until now, Con Edison had been converting alternating to direct current for the customers who needed it ??” old buildings on the Upper East Side and Upper West Side that used direct current for their elevators for example. The subway, which has its own converters, also provides direct current through its third rail, in large part because direct current electricity was the dominant system in New York City when the subway first developed out of the early trolley cars.

It’s no different with our code and hardware….. Whatever computers look like a century from now, they will, somewhere, still be running today’s code, needing to read data in today’s format, off today’s media.

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