Editing Logo (programming language) (section)

==Turtle and graphics==
{{see also|Turtle graphics}}
[[File:Tartapelago Bicicardio 01.gif|thumb|upright=1| Animated gif with turtle in [[MSWLogo]] ([[Cardioid]])<ref>{{cite web|url=http://www.maecla.it/tartapelago.htm |title=Tartapelago|first=Giorgio|last=Pietrocola |date=2005 |website=Maecla  }}</ref>]]
Logo's most-known feature is the turtle (derived originally from [[Turtle (robot)|a robot of the same name]]),<ref name="mit.edu"/> an on-screen "[[Pointer (graphical user interfaces)|cursor]]" that shows output from commands for movement and small retractable pen, together producing line graphics. It has traditionally been displayed either as a triangle or a turtle icon (though it can be represented by any icon). Turtle graphics were added to the Logo language by Seymour Papert in the late 1960s to support Papert's version of the turtle robot, a simple robot controlled from the user's workstation that is designed to carry out the drawing functions assigned to it using a small retractable pen set into or attached to the robot's body.

As a practical matter, the use of turtle geometry instead of a more traditional model mimics the actual movement logic of the turtle robot. The turtle moves with commands that are relative to its own position, ''LEFT 90'' means spin left by 90 degrees. Some Logo implementations, particularly those that allow the use of concurrency and multiple turtles, support [[collision detection]] and allow the user to redefine the appearance of the turtle cursor, essentially allowing the Logo turtles to function as [[Sprite (computer graphics)|sprites]].

Turtle geometry is also sometimes used in environments other than Logo as an alternative to a strictly coordinate-addressed graphics system. For instance, the idea of turtle graphics is also useful in [[Lindenmayer system]] for generating [[fractal]]s.