Resumen
A good user interface brings the end user face-to-face with whatever is being manipulated and experienced. The article discusses about the experience of immediacy in a programming environment which draws the programmer closer to the program. In such cases debugging is easier. The principle of immediacy can serve as a guide, keeping builders of programming environments on the path to productive environments. When programming environments convey the experience of immediacy, programmers perceive and manipulate the facets of the program and its unfolding computation with less conscious efforts and accelerate the debugging process. Authors describe how the principle of immediacy applies to debugging environments by describing ZStep 95, a program debugging environment based on the principle of immediacy. Three kinds of immediacy important for debugging, on which software designers should strive are explained in the article. These are: temporal immediacy, semantic immediacy, and spatial immediacy.

Resumen
Computers enables programmers to fashion their own universes, choosing their own sets of "physical laws." Although, may computer-based systems seem to have their physics well debugged. Some collaborative virtual environments allow their users to "program" For example, LambdaMOO at Xerox PARC allows users to make new kinds of objects with new behaviors. In virtual Kansas, nearly anything can be reprogrammed, including the computations that display objects and the mechanisms underlying arithmetic. Indeed, Kansas is a multiuser programming environment for the Self language from which it is built. In Kansas, two plus two can equal five, at least the resulting inconsistency brings the entire system crashing to halt. In cases in which the attempt to restart Kansas fails, the watcher knows to create a new world -- Oz -- with a debugger on the broken Kansas process. Users find themselves suddenly thrown into Oz, where they can collaborate in repairing the problem and then resume and reenter Kansas.