Telephone Switching System Crash
A software fault in an aging system caused a nationwide telephone outage, leaving millions without service for hours.
On January 15, 1990, AT&T's long-distance telephone switching system crashed. This was a strange, dire, huge event. Sixty thousand people lost their telephone service completely. During the nine long hours of frantic effort that it took to restore service, some seventy million telephone calls went uncompleted.
An obscure software fault in an aging switching system in New York was to lead to a chain reaction of legal and constitutional trouble all across the country. As it happened, the problem was a piece of software that had been written in C.
In the code was a long "do ... while" with a nested "switch" that had an "if" statement. The "if" contained a "break." The "break" was SUPPOSED to "break" the "if." Instead, the "break" broke the "switch" statement.
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