This legacy web site is no longer updated but will remain online for the foreseeable future. UUhistle is not being actively supported or developed. Successor systems include Jsvee and Kelmu.

UUelcome to

UUhistle (pronounced "whistle") is a tool for visually and interactively exploring the execution-time behavior of computer programs. Through UUhistle's graphics, novice programmers can improve their code-tracing skills and understanding of programming concepts and programming-language constructs.

Unlike a regular debugger, UUhistle displays challenging aspects of program execution such as parameter passing and object references in a detailed, beginner-friendly manner.

Unlike a typical program animation system, UUhistle supports an unusually interactive learning activity in which the student takes the role of the computer to execute programs.

Here's a screenshot of UUhistle in action:

screenshot of UUhistle
(Click for a larger image)

There are three main ways of using UUhistle:

Read more about UUhistle or try it out right now.