Steering programs via time travel

The environments that programmers traditionally use for problem-solving-with separate modes and tools for writing, compiling, testing, visualizing and debugging-derive their basic structure from historical accident, and take little advantage of human-computer interaction (HCI) research into the cognitive issues of programming. We believe that neglect of these issues impedes programmers´ ability to produce reliable, maintainable software. Visual programming languages (VPLs) have begun to address this problem by creating more flexible, less modal programming environments, and we have taken a step further in this direction. In this paper, we describe a VPL in which programmers can modelessly steer as they specify, visualize, explore and alter the behavior of a program while traveling through the program´s logical time. This approach supports two often-neglected cognitive principles that HCI research shows can help programmers in their problem-solving