William Orchard-Hays

The basic software for all newer computers is built on the well-established need for standard operating systems. This implies that all applications—no matter how large, complex or time consuming—must operate under (or, more precisely, on top of) the standard system. Large applications require supervisory monitors which handle problems similar to those of the operating systems, but at a different level. Sometimes, still a third or even a fourth such level is required or desirable. This leads naturally to the concept of multilevel systems—similar vertically, but different horizontally. Proper division of responsibility between levels leads to greater efficiency and less logical complexity, while actually enhancing capability.