Program debugging can be an expensive, complex and frustrating process.
Conventional programming environments provide little explicit support for
the cognitive tasks of diagnosis and visualization faced by the programmer.
ZStep 94 is a program debugging environment designed to help the programmer
understand the correspondence between static program code and dynamic program
execution. Some of ZStep 94's innovations include:
- An animated view of program execution, using the very same display
used to edit the source code
- A window that displays values which follows the stepper's focus
- An incrementally-generated complete history of program execution and
- "Video recorder" controls to run the program in forward and
reverse directions and control the level of detail displayed
- One-click access from graphical objects to the code that drew them
- One-click access from expressions in the code to their values and graphical
Henry Lieberman and Christopher Fry, Bridging
the Gap Between Code and Behavior in Programming, ACM Conference
on Computers and Human Interface [CHI-95], Denver, April 1995.
RTF Format [Microsoft Word, Mac and PC]
PostScript Format [5.3 MB]
Henry Lieberman and Christopher Fry, ZStep
95, A Reversible, Animated Source Code Stepper, in Software Visualization:
Programming as a Multimedia Experience, John Stasko, John Domingue, Blaine
Price, Marc Brown, eds., MIT Press, 1997.
RTF Format [Microsoft Word,
Mac and PC] [800 KB]
PostScript Format [2 MB]
Christopher Fry and Henry Lieberman, Programming as Driving: Unsafe
at Any Speed? Demonstration, ACM Conference on Computers and Human
Interface [CHI-95], Denver, April 1995.
Henry Lieberman, Steps Toward Better Debugging Tools for Lisp,
ACM Symposium on Lisp and Functional Programming, Austin, Texas, August
I am editing a special issue on
scheduled to appear in April 1997.
Here is the Introduction
and Table of Contents to the special issue
... and another page on Software