In this lecture from Yale's Introduction to Medical Software, the instructor introduces the medical software life cycle as the organizing principle for how a medical software project should be planned, built, and maintained. The session presents the international standard IEC 62304, which defines the required processes and documentation for medical device software development, and explains how it structures a project from initial planning through maintenance and eventual retirement. Students learn why treating development as a defined life cycle, rather than an ad hoc process, is central to meeting regulatory expectations covered earlier in the course. The lecture sets up the following sessions on how specific development methodologies fit within this standardized framework.