Winston W. Royce was an American software engineer best known for his 1970 paper “Managing the Development of Large Software Systems,” presented at IEEE WESCON. In it he drew the sequence of phases - system requirements, software requirements, analysis, program design, coding, testing, and operations - that later became known as the waterfall model, although Royce himself did not use that name.
Royce’s paper is widely misread as an endorsement of strict sequential development. In fact, after presenting the simple linear scheme he wrote, “I believe in this concept, but the implementation described above is risky and invites failure.” His point was that the basic idea was sound in outline but dangerous if applied without modification.
To make the approach work, Royce proposed five additions, including building the design twice (a pilot or prototype before the deliverable), planning and controlling documentation, involving the customer at defined points, and feeding test results back into earlier phases. He summarized these as the steps needed “to transform a risky development process into one that will provide the desired product.”
Royce worked on large software projects in the aerospace sector and led software development efforts at Lockheed. His single best-known paper has had an outsized influence: the diagram it contained shaped how generations of engineers and managers thought about the software life cycle, even as the field gradually moved toward the iterative methods Royce had himself recommended.