Before we start programming, let's take a tour of Logo to see how it works.
Logo uses a Turtle instead of a cursor:
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Logo uses three different windows. When you first run the
program you should see two windows. The top one is called the
Turtle Window - this is where the turtle draws what you tell it.
You should see the turtle in the middle of the window like this:
The other window, under the Turtle Window, is called the Logo
Window. You give commands to the turtle in this window.
It looks like:
There is one more window that Logo uses. It is called the Edit Window. You teach the turtle new things to draw in the Edit Window. We'll talk more about it later.
Now, move the mouse (arrow) into the Logo Window and click anywhere inside that window. The cursor (line) should be flashing in the window.
The Turtle knows how to do things already. You only have to tell it what you want to do.
Try this. Make certain that the cursor is on a blank line in
the Logo Window (hit the <Return> key a couple of times
if it isn't). Now type:
and hit the <Return> key. You should see:
The number 10 in the command above tells the turtle how many steps it should move forward. You can experiment to see how many steps it takes to move the turtle how you want. What else can the turtle do? Lots.
Type RIGHT 90. Don't forget to press the <RETURN> key
to give the command to the turtle. What happened?
What do you think will happen if you typed: FORWARD 10? Try it in Logo. Were you right?
Type CLEARGRAPHICS and press <RETURN>.
This command, which you can shorten to CG, clears the screen, moves the Turtle back to the center of the Turtle screen - called the Home position - and points the Turtle to the top of the screen.
Actually, many commands have abbreviations, just like CLEARGRAPHICS.
Type FD 10. What happened?
You moved FORWARD 10. So you can type FD instead of FORWARD.
Here is a list of commands the Turtle knows already:
Logo Commands |
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|---|---|
| Command(Abbreviation) | Action |
| FORWARD (FD) | moves the turtle in the direction it's facing. |
| BACKWARD (BK) | moves the turtle in the direction opposite the one it's facing. |
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CLEARGRAPHICS (CG) CLEARSCREEN (CS) |
clears the screen and moves the turtle to HOME. |
| LEFT (LT) | turns the turtle to the left. |
| RIGHT (RT) | turns the turtle to the right. |
| PENDOWN (PD) | puts the turtle's pen down; the turtle will draw when moved. |
| PENUP (PU) | picks the turtle's pen up; the turtle will not draw when moved. |
| HOME | moves the turtle to the center or origin of the drawing window. Sets the turtle heading to 0 - makes it point to the top of the screen. |
You are now ready for the next lesson!
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