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Margaret Hamilton

Original nameMargaret Hamilton

American Computer Scientist, Lead Engineer of the Apollo Moon-Landing Navigation Software

The Names Remembered · Small Roles, Famous Names

Apollo Guidance Computer SoftwareCoiner of the Term "Software Engineering"Fault-Tolerant Software Design

Who they are

Margaret Hamilton (1936– ) is an American computer scientist who led the team at the MIT Instrumentation Laboratory developing the core flight-control software for the onboard guidance computer of the Apollo Moon-landing program, and was herself one of the pioneers who first proposed using the term "software engineering" to describe how writing complex computer programs should follow rigorous engineering norms and quality standards — before this, writing programs was widely seen as a relatively casual personal-skill activity rather than a profession needing systematic engineering-management process. In 1969, at the key moment when Apollo 11 was executing the landing mission and the spacecraft was about to touch down on the Moon, the onboard computer suddenly triggered repeated program alarms from sensor data overload, and precisely thanks to the fault-tolerance and priority-handling mechanism Hamilton’s team had deliberately built into the software design, the computer was able, at the moment the alarms triggered, to automatically drop lower-priority secondary tasks and concentrate its computing resources to ensure the normal execution of the highest-priority landing task, thereby avoiding the serious consequence of the mission being forced to abort from software fault, a design thereafter proven one of the key behind-the-scenes contributors to the mission’s ultimate success. By tradition she once brought her young daughter to the lab to work overtime, and the daughter’s accidental misoperation triggered a simulated system fault, an episode that further prompted her to realize the need to design fully thorough fault-tolerance protection for a software system to handle all manner of accidental operation scenes, however low in probability.

Primary sourcesNASA Apollo guidance computer software historical archives (MIT Instrumentation Laboratory)

Key stories

The Alarm Crisis at the Last Moment of the Landing

In 1969, at the last key moment as the Apollo 11 lunar module was about to touch down on the Moon, the onboard guidance computer, from radar sensor data-processing overload, triggered repeated "1202" and "1201" program alarms, and mission control and the astronauts were for a time greatly tense; precisely because of the software priority-scheduling mechanism Hamilton’s team had carefully designed, the computer was able, at the moment the alarms triggered, to automatically drop lower-priority secondary computing tasks and fully ensure the continued normal running of the core landing task, avoiding the serious consequence of the mission being forced to abort from a software alarm.

A Daughter’s Misoperation Changed the Software Design Approach

By Hamilton’s own recollection, she once brought her young daughter to the lab to work overtime, and the daughter, playing on the simulator, accidentally entered an erroneous command combination that should not appear in a normal task flow, triggering a simulated system fault; this seemingly trivial episode made Hamilton deeply realize the need to design fully thorough fault-tolerance protection for mission-critical software to handle all manner of accidental or erroneous operations operators might make under pressure, an idea thereafter a core part of the "software engineering" methodology she advocated.

Relationships

Mentor

🖥️Grace Hopper

Echoes today

Below are how modern works borrow or reinterpret this name or story — not the original material. The two differ, so keep them apart.

The earliest proposer of the term "software engineering"Hamilton was one of the pioneers who first advocated using the term "software engineering" to stress that writing complex programs should follow rigorous engineering norms, a term thereafter a formal part of the whole discipline of computer science.

The 2016 Presidential Medal of FreedomHamilton, for her key contribution to the Apollo Moon program, was awarded the Presidential Medal of Freedom, the highest US civilian honor, in 2016.

Appears in

The Birth of the Computer and the Information AgeA Chip, a Law, and a Moon-Landing Alarm

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