In this lesson, you will learn how to give precise instructions to a robot to draw shapes on a grid. You will act like a programmer, breaking down tasks into small steps and fixing mistakes. This is like telling a computer exactly what to do, step by step. By the end, you will understand decomposition and debugging.

Ask the student "if you had to tell someone how to draw a simple shape—like a square—using only very small steps, what would you say?"

Discuss the challenge of giving precise instructions. Students will likely say, "Draw a line, then another line."

Challenge the students to give you instructions in drawing a Rectangle on the Whiteboard. Make it clear that you are following instructions precisely and exaggerate any mistakes when instructions are too vague. 

Prompt them to be more specific: "What kind of line? How long? In what direction?"

Explain to the students that today they will be acting as programmers and their job is to write a program for an "Art Bot."

This robot is very simple. It can only follow a few commands, one at a time, to draw a picture on a grid. Draw a 3x3 grid on the whiteboard.

Write the following commands on the board. These are the only words the Art Bot understands.

• MOVE_FORWARD (1) (Moves the pen forward one square)

• TURN_RIGHT (Turns the robot's direction 90 degrees clockwise)

• TURN_LEFT (Turns the robot's direction 90 degrees counter-clockwise)

• PEN_UP (Lifts the pen so it doesn't draw)

• PEN_DOWN (Puts the pen down to draw)

Collaborative Programming:

Walk through the problem as a class, writing the sequence on the board.

Step 1: "What's our first step to get to the next corner?" (Students will say "move forward").

"How many squares?" (Two squares, since the starting point is the first square). So, our first commands are MOVE_FORWARD(1), then MOVE_FORWARD(1).

Step 2: "What do we do now that we are at the corner?" (Students should say "turn right"). So, add TURN_RIGHT.

Continue this process, guiding them through the entire sequence.

The final sequence should look something like this:

Set the Challenge: Tell the students that you are going to work together to program the Art Bot to draw a square that is 3 squares by 3 squares.

MOVE_FORWARD(1)

MOVE_FORWARD(1)

TURN_RIGHT

MOVE_FORWARD(1)

MOVE_FORWARD(1)

TURN_RIGHT

MOVE_FORWARD(1)

MOVE_FORWARD(1)

TURN_RIGHT

MOVE_FORWARD(1)

MOVE_FORWARD(1)

Explain that breaking down the problem into smaller parts (like drawing one side of the square at a time) is a key part of programming called decomposition.

Can the students think of why this might be a good way to tackle problems?

Can they think of any other times they might have used/could use decomposition?