3.0 Core Command Reference: Drawing and Canvas Control
3.0 Core Command Reference: Drawing and Canvas Control
The fundamental command set in Logo provides the primary interface for instructing the Turtle to move, draw, and interact with the canvas. These commands are the essential building blocks for creating all graphical figures, from simple lines to complex illustrations. By combining these core instructions, a developer can programmatically control every aspect of the drawing process. This section documents the commands for Turtle movement, pen control, and overall canvas operations, which together form the foundation of visual programming in Logo. After mastering these, the next logical step is to manage program data using variables.
3.1 Turtle Movement Commands
These commands instruct the Turtle to move relative to its current position and heading.
| Command | Abbreviation | Function | Argument |
| forward | fd | Moves the turtle forward. | units |
| backward | bk | Moves the turtle backward. | units |
| right | rt | Turns the turtle right. | degrees |
| left | lt | Turns the turtle left. | degrees |
3.2 Pen and Turtle Appearance Control
The Turtle carries a “pen” that determines whether its movement leaves a trail. The state of this pen, along with the Turtle’s visibility, can be controlled with the following commands.
| Command | Abbreviation | Function |
| penup | pu | Lifts the pen so the turtle moves without drawing. |
| pendown | pd | Lowers the pen so the turtle draws when it moves. |
| hideturtle | ht | Makes the turtle invisible. |
| showturtle | st | Makes the turtle visible. |
| setpensize [width height] | Sets the width and height of the pen. The default pen size is [1 1]. |
3.3 Canvas and Text Commands
These commands are used to manage the drawing canvas as a whole or to display text within the Logo environment.
| Command | Abbreviation | Function |
| clearscreen | cs | Erases all drawings and resets the turtle to the center. |
| home | Returns the turtle to the center of the screen (0 0). It may leave ink behind during this movement. | |
| label | Prints a string or list of words at the turtle’s location. | |
| cleartext | ct | Clears the text region of the Commander window. |