FENCE

Tells the turtle to enter "fence" mode. From now on, if the turtle is asked to move past the boundary of the graphics window, it will move as far as it can and then stop at the edge with an "out of bounds" error message.

Compare this command with WRAP, WINDOW, and PERSPECTIVE.

WRAP
FORWARD 950
RIGHT 90
FENCE
FORWARD 950
turtle out of bounds
FORWARD 100
turtle out of bounds
BACK 500