Logo Programming Language

Although Logo contained a great deal of numerically related commands and capabilities, it became best known for the graphics producing robot character (essentially a commandable graphics cursor). The robot was later called the "Turtle Robot", or simple the "Turtle". Not only did educational games and teaching applications focused heavily on using the Turtle, some implementations of Logo did not include most other features and even eliminated everything but turtle graphics.

The robot, was conceived as a way to encourage students to think about the computer code as if they were the robot receiving the instructions. The student was encouraged to visualize where they would travel and what they would draw along the path, then see what actually happened when the code was executed. Again, this was merely one of many intended aspects of the language.

Example code:
(define COLORS1 (list "red" "green" "yellow" "purple"))

(define (spiral a x times)
(if (< times 0)
empty
(append (list (forward x)(turn-left a))
(spiral a (+ x 2)(sub1 times)))))

(define spiral-image
(list (change-pen-size 2)
(change-bg-color "black")
(change-color COLORS1)
(spiral 91 1 152)))
(draw spiral-image)

The above code produces this: