A pedagogical model of hypertext authoring is presented. The model encourages self-regulated, constructive thinking to create knowledge by manipulating corresponding screen representations. One application of the design-oriented model is described, with screen illustrations. (MSE)

PLUS, an authoring system designed to develop cross-platform courseware for different computer types, was evaluated for its portability (ability to run on multiple platforms without adjustment). The procedures and computer equipment used are described, and results are presented. It is concluded that PLUS produces highly portable programs. (MSE)

The use of cellular automata to analyze several pre-Socratic hypotheses about the evolution of the physical world is discussed. These hypotheses combine characteristics of both rigorous and metaphoric language. Since the computer demands explicit instructions for each step in the evolution of the automaton, such models can reveal conceptual…