ABSTRACT
Most versions of Logo have a single graphic object, the turtle, which can be moved around on the screen. This is fine for most drawing applications, but it becomes a limitation if you want to model objects that interact in some way. In a simulation of animal behavior, for example, you might want to write Logo procedures to simulate the behavior of a predator looking for food and its prey seeking to avoid being eaten, and then run them together to see how they fare. And, of course, it is hard to write programs for any kind of video game with only one graphic object.
