Turtle graphics Turtle graphics provide a manner to draw figures in the two-dimensional real plane. For this purpose, the plane is equipped with a so called turtle , which can be imagined as a simple robot that can move around in the plane. Turtles are equipped with pens , with which a turtle can draw a line while moving from one position to another. A turtle may have many different colored pens, but can only use one color per drawn line. Selecting a color is controlled by special turtle commands.
Turtles have a memory, in which they store certain bits of information.
Turtle spaces have additional features. Every turtle space is equipped with a turtle stack in which at arbitrary moments turtles can be stored, and from which turtles can be retrieved. Most turtle spaces also use so called cyclotomy , which means that the direction that a turtle can point to is confined to a finite set of predefined angles. The L -system produces a sequence of strings consisting of variables and constants, where the constants consist of turtle commands. The variables are ignored by the turtle, with two exceptions, the F and f command.