Turtle Graphics

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Turtle graphics is a term in computer graphics for a method of programming vector graphics using a relative cursor (the "turtle") upon a Cartesian plane. Turtle graphics is a key feature of the Logo programming language.

The turtle has three attributes:

a location
an orientation
a pen, itself having attributes such as color, width, and up versus down.

The turtle moves with commands that are relative to its own position, such as "move forward 10 spaces" and "turn left 90 degrees". The pen carried by the turtle can also be controlled, by enabling it, setting its color, or setting its width. A student could understand (and predict and reason about) the turtle's motion by imagining what they would do if they were the turtle. Seymour Papert called this "body syntonic" reasoning.

From these building blocks one can build more complex shapes like squares, triangles, circles and other composite figures. Combined with control flow, procedures, and recursion, the idea of turtle graphics is also useful in a Lindenmayer system for generating fractals.

Turtle geometry is also sometimes used in graphics environments as an alternative to a strictly coordinate-addressed graphics system.