Behavioral Aspects of Text Editors

Theoretical models and experimental results relevant to the study of behavioral issues in the use of text editors--including both those intended primarily for computer program development and those intended for manuscript preparation--are examined. Models can predict editing task time in terms of elementary activities, in an error-free environment, to an accuracy comparable to the variability between subjects. In a realistic setting, however, unpredictable user activities account for between 25 and 50 percent of the task time, an amount that is comparable to individual variations due to errors. Variations in computer response time appear to affect users more than mere delay does. Command options improve expert performance but degrade the performance of beginners. The surface syntax of an editor can have considerable impact on ease of use. Ergonomic aspects of keyboard and display terminal design and use are well understood, with little hope for significant improvement, but there is no experimental evidence to support guidelines for display format design. Among analog pointing devices the mouse appears to have a small edge over the light pen, joystick, and track ball; human pointing performance using these devices approaches known psychophysical limits. Optimum ambient conditions, including temperature, noise, work-station layout, illumination, and work-rest cycles derived for professional key entry operators and for other interactive tasks, are probably also valid for editing. Gaps in the application of cognitive psychology and human engineering to text editors in the literature are indicated, and promising research areas are delineated.