A Computer Architecture for Level Structured Systems

The notion of level structured operating systems is receiving growing acceptance in the computing community. These systems are implemented and debugged incrementally, one level at a time. Each level provides a pseudo-machine interface upon which the next level can be implemented. Such systems offer significant advantages from the piont of view of debugging, reliability, understandability, and modifiability over conventionally organized systems. The efficiency price which must be paid for this type of organization can be overcome by providing some simple mechanisms in the hardware to support the level structure. It is the purpose of this paper to point out where the hardware support is needed and to suggest one way of implementing these features.