Neil Armstrong hovered a few miles above the surface of the moon on July 20, 1969, searching for a safe place to make history.
Only minutes of fuel remained to land the first men on another world. A power meter failed in Apollo 11's cramped lunar lander. Communications faded in and out. Then, warnings began flashing: Program alarm. Program alarm.
Five times the onboard computer signaled an emergency like none Armstrong and crewmate Buzz Aldrin had practiced.
In that moment, the lives of two astronauts, the efforts of more than 300,000 technicians, the labor of eight years at a cost of $25 billion, and the pride of a nation depended on a few lines of pioneering computer code.
Humans had never risked so much on zeros and ones. Yet they decided to trust the machine and the binary two-digit code, and Armstrong and Mr. Aldrin reaped the glory as the first people to walk on the moon.
"The software saved the mission," says Fred Martin, 85, who managed much of the Apollo software development.
From The Wall Street Journal
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