Three Criteria for Designing Computing Systems to Facilitate Debugging.

The designer of a computing system should adopt explicit criteria for accepting or rejecting proposed system features. Three possible criteria af this kind are input recordability, input specifiability, and asynchronous reproducibility of output. These criteria imply that a user can, if he desires, either know or control all the influences affecting the content and extent of his computer's output. To define the scope of the criteria, the notion of an abstract machine of a programming language and the notion of a virtual computer are explained. Examples of applications of the criteria concern the reading of a time-of-day clock, the synchronization of parallel processes, protection in multipragrammed systems, and the assignment of capability indexes. [ABSTRACT FROM AUTHOR]