Universal Systems Language

Universal Systems Language (USL) is a systems modeling language and formal method for the specification and design of software and other complex systems. It was designed by Margaret Hamilton based on her experiences writing flight software for the Apollo program. The language is implemented through the 001 Tool Suite software by Hamilton Technologies, Inc. USL evolved from 001AXES which in turn evolved from AXES all of which are based on Hamilton's axioms of control. The 001 Tool Suite uses the preventive concept of Development Before the Fact (DBTF) for its life-cycle development process. DBTF eliminates errors as early as possible during the development process removing the need to look for errors after-the-fact.

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