Edsger Dijkstra reported on his efforts to design a computer system with a layered approach. Edsger worked at the University of Technology of the Netherlands and published his report in 1969. In his report he described the workings of a computer system that he simply called the "THE". The term "THE" was an acronym for Technische Hogeschool Eindhoven. His research was conducted by a small group of to notch people and he made mention that his design could only succeed with that of only the brightest of people. Though his team was small, consisting of six people, they all held either a Masters degree or a PH.D. Dijkstra also makes note that it was imperative that his entire team devoted all of their time to the project as he said that giving only part time would result in nothing less than poor inefficient work.
The "THE" system was designed on a layered architecture which made testing and debugging less complicated. The layered architecture allowed only the layers directly adjacent to each other, the ability to communicate. This approach was much more systematic and allowed the team to isolated problems one layer. This in turn simplified the efforts needed to debug the system.
Their system was made of five layers labeled zero to five. Layer zero was the lowest level dealing with CPU access and interrupts. Layer one was to deal with allocating memory while layer two handled the operating systems communications. Layer three handled input and output for each device connected to the machine. Layer four was to handle user built application requests and lastly layer five was simply the end user their-selves. The entire purpose of the layers was that an upper layer would only depend on the layer directly below it.