Between 1961 and 1963, Margaret Hamilton began to study software reliability while she was working at the US SAGE air defense system. In 1965, she was responsible for programming the software for the onboard flight software on the Apollo mission computers. After Hamilton had completed the program, the code was sent to Raytheon where "expert seamstresses" called the "Little Old Ladies" actually hardwired the code by threading copper wire through magnetic rings. Each system could store more than 12,000 words that were represented by the copper wires.