John F. Pane

Studying the language and structure in non-programmers' solutions to programming problems

Programming may be more difficult than necessary because it requires solutions to be expressed in ways that are not familiar or natural for beginners. To identify what is natural, this article examines the ways that non-programmers express solutions to problems that were chosen to be representative of common programming tasks. The vocabulary and structure in these solutions is compared with the vocabulary and structure in modern programming languages, to identify the features and paradigms that seem to match these natural tendencies as well as those that do not. This information can be used by the designers of future programming languages to guide the selection and generation of language features. This design technique can result in languages that are easier to learn and use, because the languages will better match beginners existing problem-solving abilities.

Using HCI techniques to design a more usable programming system

A programming system is the user interface between the programmer and the computer. Programming is a notoriously difficult activity, and some of this difficulty can be attributed to the user interface as opposed to other factors. Historically, the designs of programming languages and tools have not emphasized usability. This paper describes the process we used to design HANDS, a new programming system for children that focuses on usability, where HCI knowledge, principles, and methods guided all design decisions. The features of HANDS are presented along with their motivations from prior empirical research on programmers and new studies conducted by the authors. HANDS is an event-based language that features a concrete model for computation, provides operators that match the way non-programmers express problem solutions, and includes domain-specific features for the creation of interactive animations and simulations. In user tests, children using HANDS performed significantly better than children using a reduced-feature version of the system where more traditional methods were required to solve tasks.

Assessing dynamics in computer-based instruction

We present an evaluation of a multimedia educational software system that includes text, graphics, animations, and simulations. When compared with an informationally equivalent control environment that used text and carefully selected still images, we found little evidence that the dynamic presentations enhanced student understanding of the declarative information in this lesson. Furthermore, students cannot be relied on to take fllll advantage of exploratory opportunities in computer-based instruction. These results prescribe further investigation of whether and how computer-based multimedia can be used effectively in education and training.

Evolution of Novice Programming Environments: The Structure Editors of Carnegie Mellon University

Abstract Beginning in the early 1980s, the Computer Science Department at Carnegie Mellon University developed and used three generations of novice programming environments. The focus of these systems was to apply, advance and tune structure editor technology in support of the teaching and learning of computer programming. The use of these pedagogical systems in Carnegie Mellons introductory programming courses provided feedback and inspiration to guide the projects. This paper tracks the evolution of the programming environments and courses, documenting important lessons and discoveries about novice programmers and the environments that support them.

Tabular and textual methods for selecting objects from a group

The accurate formulation of boolean expressions is a notorious problem in programming languages and database query tools. This paper studies the ways that untrained users naturally express and interpret queries, revealing some of the underlying reasons why this task is so difficult. Among the studys findings are: people interpret the word AND to mean either conjunction or disjunction depending on context, the scope to which they attribute the word NOT depends on whether the subsequent operator is AND or OR, and they often ignore parenthesis. Therefore, relying on these words and symbols for query formulation will result in poor usability. A tabular query form is proposed that avoids the need to name the operators, provides a clear distinction between conjunction and disjunction, and makes grouping more explicit. Comparing the tabular language with textual boolean expressions, the study finds that untrained users perform better when they express their queries in the tabular language, and about equally well when interpreting queries written in either language. We conclude that systems may benefit by adopting a tabular notation for query formulation.

Analyzing graphic and textual layouts with GOMS: results of a preliminary analysis

We combined previous research on GOMS modeling with some simple assumptions about visual search strategies to make zero-parameter predictions of the time necessary to perform a task on four different graphic and textual displays. We compared these predictions to empirical measures of performance time and obtained an absolute average percent difference of 8%. These results indicate that GOMS may be extended to be a useful tool for analyzing different layouts. KEY WORD S: GOMS, cognitive modeling, graphic layout, textual layout. INTRODUCTION Previous studies have shown GOMS to be a powerful and accurate method of analysis for human performance [e.g., [1, 2]. Despite the wealth of studies that have been performed with GOMS, there has been little or no effort directed towards extending it to model efficiency differences with various graphic and textual layouts. The primary reason for this is because the syntax of GOMS was not sufficiently fine-grained for such differences to become apparent. Recently however, GOMS was expanded to model tasks with low level perceptual, cognitive and motor operators [e.g., 5]. This opens up the possibility of using GOMS to compare different layouts. Such an analysis would be very useful in testing newly developed user interfaces. In addition, it can also be used to provide heuristics and highlight problems in automatic visualization systems. THE TASK We modeled Casner’s task of finding information about airline flights [3,4] In particular, the user had to fiid a pair of connecting flights that travel from Pittsburgh to Mexico City, such that the flights are available, the layover is no longer than four hours, and the combined cost of the flights do not exceed

Improving user performance on Boolean queries

500. Casner presents four examples of graphical layouts that present the required information: 1) tabular layout, where the rows contain information for Permission to copy without fee all or pert of this material is granted provided that the copies are not made or dktributad for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, end notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee andior specific permission. CH194 Companion-4/94 Boston, Massachusetts USA e 1994 ACM 0-89791 -651 -4/94 /0323 ..

The impact of human-centered features on the usability of a programming system for children

3.50 each flight and the columns represent origin, destination, availability, price, departure time and arrival time; 2) graphical layout that represents individual flights as rectangles on a timeline. Cost and availability is encoded as text inside the rectangles. The right-edge of each rectangle encc~des departure time, the left-edge encodes arrival time and the length of the rectangle encodes flight duration; 3) graphical layout that is similar to (2) but uses shading to incticate availability and finally 4) graphical layout that is similar to (3) but uses the height of the rectangle to indlicate pricel. THE MODEL There are many different strategies for accc)mplishing the task specifkl above. In [3], Casner examines eight different algorithms for the task. These algorithms capture different types of spatial searches but by no means exhaust all possible task methods. A complete analysis of the layouts would try to iclentify and model a reasonable set of all the possible algorithms (as John, et.al. did in [6]) or empirically determine which strategies are actually used, However, to limit the scope of this preliminary analysis, we modeled a single straightforward, efficient algorithm for each layout. We realized these algorithms as a series of GOMS operatcrs that, given the particular task and display, solve the task. In particular, the most important task operation for differentiating between the layouts, the visual search, was modeled with the combinations of cognitive, motor and perceptual operators proposed in [5]. We assigned a duration to each GOMS operator base[i on previous psychological studies [2, 5]. We then added the durations of operators together appropriately to get a zero-parameter prediction of performance time for each display layout. Since previous GOMS modeling did nolt include any guidance for predicting the duration or pattern of visual search that am based on display layout (i~s opposed to functional requirements of the task), we adopled Tunis’ ruleof-thumb that all information grouped within 5 degrees of visual angle can be perceived in a single eye fixation [7]. Assuming that the user was approximately 15 inches from the screen,5 degreesof visual angle is equal to 0.65 inches, which corresponds to approximately six 12 point characters. 1 Layout 4 was constructed by Casner’s automatic visualization system, BOZ.

The design view: a design oriented, high-level visual programming environment

The accurate formulation of boolean expressions is a notorious problem in programming languages as well as database and web query tools. Users have demonstrated great difficulty with the common textual method for specifying these queries, which uses the boolean operators AND, OR, and NOT, partly because these words are used inconsistently in natural languages. This paper proposes a tabular boolean query language that avoids the need to use named operators, provides a concrete distinction between conjunction and disjunction, and makes grouping more explicit. A study comparing this tabular language with textual boolean expressions found that untrained users perform better when they express their queries in the tabular language, and about equally well when interpreting queries written in either language. We conclude that systems can benefit by adopting a tabular notation for query formulation.

Designing a programming system for children with a focus on usability

HANDS is a new programming system for children that was designed for usability. This paper examines the effectiveness of three features of HANDS: queries, aggregate operations, and data visibility. The system is compared with a limited version that lacks these features. In the limited version, programmers can achieve the same results but must use more traditional programming techniques. Children using the full-featured HANDS system performed significantly better than their peers who used the limited version. This provides evidence that usability of programming systems can be improved by including these features.