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fd number
(forward)
= used for the observer, = used for turtles, 
= used for patches
Commands to:
Move Turtles,Clear & Setup,
Color,Create Turtles
Other Commands
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Moves turtles backward by number steps.
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fd number
(forward)
Moves turtles forward by number steps.
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jump number
Moves turtles forward by number units in one "big step" (in one unit of time).
This command is useful for synchronizing turtle movements. The command fd 15 takes
15 times longer to execute than fd 1, but jump 15 executes in the same time
as jump 1 or fd 1.
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heading
heading-of ID-number
heading reports the heading of the turtle. Heading 0 is due north, 90
is east, and so on.
heading-of reports the heading of the turtle with the given ID-number.
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home
Moves the turtle to the middle of the screen, at coordinates (0, 0).
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lt number
Turns turtles left by number degrees.
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rt number
Turns turtles right by number degrees.
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distance x-coordinate y-coordinate
distance-nowrap x-coordinate y-coordinate
Reports the distance to the point (x-coordinate, y-coordinate)
With distance, turtles and patches use the "wrapped distance" (around the edges of the
screen) if that distance is shorter than the "onscreen distance." With distance-nowrap,
turtles and patches always use the onscreen distance.
Example:
if (distance 0 0) > 10 [setc green]
(All turtles more than 10 units from the center of the screen turn green.)
seth number turtles, patches
(set heading)
Sets the heading of turtles to number. Heading 0 is due north, 90 is east, and so on.
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setx number
Sets the x-coordinate of turtles to number.
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setxy number1 number2
Sets the x-coordinate of turtles to number1 and the y-coordinate of turtles to
number2.
Example:
setxy 0 0
(All turtles move to the center of the screen.)
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sety number
Sets the y-coordinate of turtles to number.
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towards x-coordinate y-coordinate
towards-nowrap x-coordinate y-coordinate
Reports the direction from the turtle towards the point (x-coordinate, y-coordinate).
If the "wrapped distance" (around the edges of the screen) is shorter than the "onscreen
distance," towards will report the direction of the wrapped path, while
towards-nowrap will report the direction of the onscreen path.
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turtle-at x-offset y-offset
Reports the ID-number of another turtle in the patch that is x-offset away in the
x-direction and y-offset away in the y-direction. If there are several turtles in
the patch, an arbitrary (other) turtle is picked.
If used by a patch, and there are no turtles in the indicated patch, reports -1. If used by
a turtle, and there are no other turtles in the indicated patch, reports -1.
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turtle-here
Reports the ID-number of another turtle in the same patch. If there are several turtles in
the patch, an arbitrary (other) turtle is picked.
If used by a patch, and there are no turtles in the patch, reports -1. If used by a turtle,
and there are no other turtles in the patch, reports -1.
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turtles-at x-offset y-offset
Reports the number of turtles in the patch that is x-offset away in the x-direction
and y-offset away in the y-direction.
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turtles-here
Reports the number of turtles in the patch.
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turtle-total
Reports the total number of turtles.
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who
Reports the ID-number of the turtle.
Example:
if who < 50 [setc blue]
(Makes 50 of the turtles blue.)
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xcor
xcor-of ID-number
xcor reports the x-coordinate of a turtle or a patch.
xcor-of reports the x-coordinate of the turtle with the given ID-number.
Example:
sety xcor
(Sets turtlesı y-coordinate to equal x-coordinate, so that all turtles move to the line y=x.)
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ycor
ycor-of ID-number
ycor reports the y-coordinate of a turtle or a patch.
ycor-of reports the y-coordinate of the turtle with the given ID-number.
Example:
setpc ycor
(Displays the StarLogo color table as horizontal bands.)
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Kills all turtles, sets the color of all patches to black, and clears the Plot Window.
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cc
(clear commands)
Deletes all text in the command center.
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cg
(clear graphics)
Sets the color of all patches to black.
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screen-edge
Reports the maximum x-coordinate (and maximum y-coordinate). This is the "half width"
of the StarLogo world. (The full width is actually (2 * screen-edge) + 1.)
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screen-size
Reports the width (or height) of the StarLogo world. (In the current version, the StarLogo
world is always a square, so the width and height are always the same.) You can change the
size by changing the starlogo.patch file (see section 1.4).
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show thing
Prints thing in the command center.
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color reports the color of a turtle.
If used by a patch, color reports the color of the turtle on the patch. If there are
several turtles on the patch, it arbitrarily chooses one of them. If there are no turtles
on the patch, it reports the patchıs color.
color-of reports the color of the turtle with the given ID-number.
color-at reports the color of a turtle in the patch (dx, dy) units away. If
there are several turtles on the patch, it arbitrarily chooses one. If there are no turtles
on the patch, it reports the patchıs color.
Example:
if color = white [fd 20]
(Moves all white turtles forward 20 steps.)
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pc
(patch color)
pc-at dx dy
pc reports the color number of a patch.
pc-at reports the color of the patch (dx, dy) units away.
Example:
if pc = white [fd 20]
(All turtles on top of white patches move forward 20 steps.)
if pc = red [setpc blue]
(All red patches turn blue.)
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pd
(pen down)
Puts down the turtle's pen, so that the turtle draws (leaves a trail) when it moves.
The turtle draws by changing the color of the patches underneath it to its own color.
To change the color of the turtleıs pen (and the color of the turtle itself), use setc.
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pu
(pen up)
Lifts up the turtle's pen, so that the turtle doesn't draw when it moves. To put down
the turtle's pen, use pd (for pen down).
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setc color
setc-of ID-number color
setc-at dx dy color
setc sets turtle's color to the given color. See section 3 for discussion
of StarLogo colors.
setc-of sets the color of the turtle with the given ID-number.
setc-at is used by a turtle to set the color of turtles in the patch (dx, dy)
units away.
Example:
setc red
(Each turtle turns red.)
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setpc color
setpc-at dx dy color
setpc sets patch's color to the given color. See section 3 for discussion
of StarLogo colors.
setpc-at is used by a patch to set the color of the patch (dx, dy) units away.
Example:
setpc green
(Each patch turns green.)
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stamp color
stamp-at dx dy color
stamp sets the color of the patch under the turtle to the given color.
See section 3 for discussion of StarLogo colors.
stamp-at is used by a turtle to set the color of the patch (dx, dy) units away.
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Creates number new turtles. New turtles start at position (0, 0).
[Explain initial color and headings.]
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hatch procedure-list
Each turtle creates a new turtle, identical to itself, and tells the new turtle to
execute procedure-list.
Example:
hatch [lt 45] hatch [rt 45]
(Each turtle creates two new turtles, one angled to the left, one angled to the right.)
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alive?
alive?-of ID-number
alive? reports true if the turtle is alive. alive?-of reports true if turtle with the
given ID-number is alive.
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die
Tells turtles to die.
Example:
if pc = red [die]
(All turtles on red patches die.)
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If predicate evaluates to true, then execute procedure-list.
Example:
if xcor > 0 [setc blue]
(Turtles on the right half of the screen turn blue.)
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ifelse predicate proc-list1 proc-list2
If predicate evaluates to true, then execute proc-list1. If
predicate evaluates to false, then execute proc-list2.
Predicate may have different values for different objects, so some objects may
execute consequent-procedure while others execute alternate-procedure.
Example:
ifelse xcor > 0 [setpc blue] [setpc red]
(The left half of the screen turns red and the right half turns blue.)
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repeat number procedure-list
Executes procedure-list number times.
Example:
pd repeat 36 [fd 1 rt 10]
(Each turtle draws a circle.)
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