information visualization, information physics. We describe the current status of Pad++, a zooming graphical interface that we are exploring as an alternative to tradhional window and icon-based approaches to interface design. We discuss the motivation for Pad++, describe the implementation, and present prototype applications. In addition, we introduce an informational physics strategy for interface design and briefly compare it with metaphor-based design strategies.

Software visualization is the use of interactive computer graphics, typography, graphic design, animation, and cinematography to enhance the interface between the software engineer or the computer science student and their programs. Although several taxonomies of software visualization have been proposed, they use few dimensions and do not span the space of important distinctions between systems. We attempt to fill this gap in the literature by proposing a novel and systematic taxonomy of six areas making up thirty characteristic features of software visualization technology. The taxonomy is presented and illustrated in terms of its application to seven systems of historic importance and technical interest.

Software is invisible, disappearing into files on disks. The invisible nature of software contributes to low programmer productivity by hiding system complexity, particularly for large team-oriented projects. Visualization can help software engineers cope with this complexity and thereby increase programmer productivity. We describe four innovative visual representations of software that scale to productionsized systems and illustrate their usage in five software case studies involving: version history, differencing, static properties, performance profiles, and dynamic program slices. Keywords: software visualization, legacy code, version history, program comparison, profiling, slicing. 1 Introduction It is well known that large computer programs are complex and difficult to maintain. Production-sized systems, particularly legacy software, may contain millions of lines of code. Even a seemingly simple, small-team software project, such as a spreadsheet, is very complicated [CE94]. ...

user interface management system (UIMS). We describe Pad++, a zoomable graphical sketchpad that we are exploring as an alternative to traditional window and icon-based interfaces. We discuss the motivation for Pad++, describe the implementation, and present prototype applications. In addition, we introduce an informational physics strategy for interface design and briefly contrast it with current design strategies. We envision a rich world of dynamic persistent informational entities that operate according to multiple physics specifically designed to provide cognitively facile access and serve as the basis for design of new computationally-based work materials. 1 To appear in the Journal of Visual Languages and Computing.

In this paper, we explore the question of whether program understanding tools enhance or change the way that programmers understand programs. The strategies that programmers use to comprehend programs vary widely. Program understanding tools should enhance or ease the programmer's preferred strategies, rather than impose a fixed strategy that may not always be suitable. We present observations from a user study that compares three tools for browsing program source code and exploring software structures. In this study, 30 participants used these tools to solve several high-level program understanding tasks. These tasks required a broad range of comprehension strategies. We describe how these tools supported or hindered the diverse comprehension strategies used.

This research was partially sponsored by NCCOSC under Contract No. N66001-94-C-6037, Arpa OrderNo. B326, and partially by NSF under grant number IRI-9319969. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official poli-cies, either expressed or implied, of the U.S. Government.

Much of software developers’ time is spent understanding unfamiliar code. To better understand how developers gain this understanding and how software development environments might be involved, a study was performed in which developers were given an unfamiliar program and asked to work on two debugging tasks and three enhancement tasks for 70 minutes. The study found that developers interleaved three activities. They began by searching for relevant code both manually and using search tools; however, they based their searches on limited and misrepresentative cues in the code, environment, and executing program, often leading to failed searches. When developers found relevant code, they followed its incoming and outgoing dependencies, often returning to it and navigating its other dependencies; while doing so, however, Eclipse’s navigational tools caused significant overhead. Developers collected code and other information that they believed would be necessary to edit, duplicate, or otherwise refer to later by encoding it in the interactive state of Eclipse’s package explorer, file tabs, and scroll bars. However, developers lost track of relevant code as these interfaces were used for other tasks, and developers were forced to find it again. These issues caused developers to spend, on average, 35 percent of their time performing the mechanics of navigation within and between source files. These observations suggest a new model of program understanding grounded in theories of information foraging and suggest ideas for tools that help developers seek, relate, and collect information in a more effective and explicit manner.

There are many examples of text databases including literary corpora and computer source code where statistics are associated with each line. A visualization technique for this class of data represents the text lines as thin colored rows within columns. The position, length, and indentation of each row corresponds to that of the text. The color of each row is determined by a statistic associated with each line. The display looks like a miniature picture of the text with the color showing the spatial distribution of the statistic within the text. Using this technique, SeeSoft™, a dynamic graphics software tool, can easily display 50,000 lines of text simultaneously on a high-resolution monitor. 1.

Visualizations of software changes are presented that complement existing visualizations of software structure. The principal metaphors are matrix views, cityscapes, bar and pie charts, data sheets and networks. Linked by selection mechanisms, multiple views are combined to form perspectives that both enable discovery of high-level structure in software change data and allow effective access to details of those data. Use of the views and perspectives is illustrated in two important contexts: understanding software change by exploration of software change data and management of software development.

SeeSys TM is a system embodying a technique for visualizing statis-tics associated with code that is divided hierarchically into subsystems, directories, and les. This technique can display therelative sizes of the components in the system, the relative stability of the components, the location of new functionality, and the location of error-prone code with many bug xes. Using animation, it can display the historical evolution of the code. Applying this technique, the source code from amulti-million line production software product is visualized.