Drawing basic shapes, lines and curves

The basic tool used for drawing shapes is the small triangle that appears in the center of the screen and is traditionally called "the turtle." By typing instructions in the command line we "tell" the turtle what to do. For example issuing the command FD 50 causes the turtle to move 50 small steps (pixels) forward while drawing a line. By typing CIRCLE 34, the turtle draws a circle of diameter 34 centered around its new location. By typing JT 30 100 the turtle "jumps" (without drawing a line) to the new location (30,100) where x=30 and y=100. Another way to "tell the turtle what to do" is to use the mouse and the mouse interface but in this course we will focus on typing commands directly.

The are two places to type commands. The command line and the editor.

The command line lies between the drawing screen and the editor. It is possible to enlarge a screen by clicking the Undock button that is above the top right corner of the screen. When you type a SeeLogo command on the command line something usually happens in the drawing screen and the command also appears in the editor. Thus a picture you draw corresponds to a group of commands. Every picture has a name. that appears in the small "Names" menu that is located to the left of the editor. The first name is created automatically when Seelogo starts and is called "First". The NEW command is used to create new names and it must follow by a specific name. Here is an example with explanations.

Start SeeLogo and type:

GOFD 50 <enter>

CIRCLE 30 <enter>

NEW HOO <enter>

JT 100 40 STAR 5

Now click on the first name and see the first picture and the commands in the editor that correspond to it. Next click on the name HOO and see the other picture and commands.

Now it time to learn some commands systematically

The fundamental shapes in SeeLogo are:

• Closed shapes (Rectangle, Circle and Star)

• Lines

• Arcs and Curves