1.4: Variables

Step 1

Getting Started

PRE-FLIGHT WARNING

Our drones are durable, yet not indestructible. Please exercise caution while piloting your drone. To prolong the longevity of your drone, avoid flying into walls or other objects. Prior to takeoff, please review lesson 0.2 “Before You Fly”.

Make sure that your drone is connected with Blockly before starting the lesson! If you are unsure of how to connect, go back to the first lesson to review!

Step 2

What are Variables?

Variables are a way to store information in a program, and they’re used most often to store values. If you’re playing a video game, there’s a variable to store your score, another one for your lives, and maybe another one for experience points. With your CoDrone EDU, you might use them to store the value of a sensor, the speed of your drone, or maybe how far it will go.

Variables are especially beneficial if a value appears multiple times in your program. Take a look at the following square code from the previous lesson. What would you have to do to make the square bigger? How can a variable solve this problem?

Step 3

Create a Variable

To create a variable, go to the pink variables menu in Blockly and click on the Create variable… button.

Next, you have to name your variable. In programming, it is important that your variable name is short and descriptive. For now, we will use a common variable you have probably used in your math class before. Name your variable “x”.

CoDrone Blockly new variable name prompt

For every new variable you create, you will see a set of blocks created in the “Variables” menu for you to use.

Step 4

Initializing a Variable

To initialize a variable means to assign the variable to a value. In this course, you will normally set variables to a number, but there are other variable types as well that you will learn about in a future lesson. Drag the set block with your variable to the workspace.

Set the variable “x” to a number by accessing the “Math” menu and dragging in the number block.

Then, change the 0 value to any number.

Step 5

Access the Variable

When you need to use the value that is stored in the variable, you can use the block with the variable name. In the example below, we are setting a new variable “y” to 5.

Try out the example code to see what happens!

Step 6

Print the Variable

A good tool to know for debugging variable values is the print block. The print block can be found inside the “Input/Output” menu.

Connect a variable or any block that returns a value to see the value in the console window. Add a print block to your program and connect it to the block that retrieves the “y” value.

Step 7

Using Variables in Flight

Now that you know the basics of using variables, let’s use variables to improve the square program. Open or create a program that will fly CoDrone EDU in a square shape. Use the default go values like this:

Run your code and observe its behavior. Then, create a new variable “seconds” and set it to 1 at the top of your square program.

Find every part in your code that uses the number 1 to program a flight duration. Now that you have a variable, you can replace each of these duration parameters with the variable block for seconds. Drag and drop the variable block directly into the seconds parameter.

Now, repeat for all seconds parameters.

Run the code again and notice that it runs the exact same way as before!

Step 8

Change the Variable

What would you do to make the square bigger? In the original program without variables, you would need to change every go block. Now, you only need to change the variable value, and it will be applied for the entire program. Make the square bigger by changing the value to 2. Make sure to clear a space that’s large enough for your new flight path.

Step 9

Spiraling Square

To change a variable value in the middle of a program without user input, you can use the change by block. This block will increase or decrease the value of the variable by the number you input. For example, this program increases the length of each side by 0.5 seconds for each side of the square. Draw the flight path on paper. What does it look like?

Step 10

Challenge

Challenge: More Variables!

From your square program, add other variables for duration, power, and degrees. What kinds of flight patterns can you create?

Step 11

Lesson Complete

Let’s review what you learned about variables so far! You can use variables to hold values for the CoDrone EDU to use in the program. In the activities above, you got to see how to save values in a variable and use them with other blocks.

This lesson works with:

Grade level:

Approx. time required:

CSTA

CCSS