Introduction to Variables
In this lesson, you will learn how to create and use variables in RoboBlocky. This video explains why variables are useful, how to declare and name them, and how to assign values. It also shows how to use variables in code, update their values, and print them to the console.  

 

 

1. Why Do We Store Values?

When we write programs, we often need to store values to use them later or in more than one place.

For example, imagine you want your robot to trace a square. You might use four driveDistance blocks, each with the same number to represent the side length. If you want to change the size of the square, you would have to change all four blocks one by one.

Instead, you can store the number in one place and use it in all four blocks. That way, if you want to change it, you only have to change it once. You do this by creating a variable.

 

2. What Is a Variable?

A variable is a place in a program where you can store a value, such as a number. You can think of it like a labeled container or a storage box. The label is the name of the variable, and what is inside the box is the value.

For example, you might create a variable called sideLength and store the number 4 in it. Then, you can use sideLength in different parts of your program instead of writing the number 4 over and over again.

 

3. How to Create or “Declare” a Variable

We create a variable using the set variable block, found in the Variables block menu.

 

Click the drop-down menu to see many options. Select "New variable" to create a new variable and give it a name. Creating a variable and giving it a name is also called declaring a variable.

 

4. Give the Variable a Descriptive Name

It is good practice to use names that tell you what the variable is for. For example, distance, height, or sideLength.

Variable names:

• Can have numbers in them (like distance2)
• Should not start with a number (avoid 2distance)
• Should not have spaces (use sideLength or side_length, not side length)

 

5. Assign a Value to the Variable

To store a value in a variable, attach a blue number block to the set variable block. This is also known as assigning a value to the variable. In this example, the variable named distance has an assigned value of 4.

 

6. Using a Variable

After we create a variable, it will show up in the Variables block menu.

 

Note: If the newly created variable does not appear right away, click the Variables menu button twice to refresh it.

We can now drag the variable block into other code blocks that use a blue number block, like the driveDistance block.

This driveDistance block will drive the robot the number of inches stored in the distance variable.

 

7. Variables Can Change During a Program

The word "variable" comes from the fact that its value can vary, or change. You can update a variable's value later in the program using another set variable block.

This can be seen in Example 1, where the distance variable is first assigned a value of 6, and then changed later in the program to a value of 4.

 

8. Printing a Variable

We can use the print variable block to print the name of a variable and its value.

For example, if the variable is named distance and its value is 8, the message printed in the console will be: "distance is 8".

 

9. What Happens Behind the Scenes?

When you create a variable, the computer sets aside space in its memory to store the value. Memory is the part of a computer where data is stored so the program can use it later. Data is the information the computer uses or stores, such as numbers, text, or images.

Different types of data take up different amounts of memory. A long number may take up more space than a short one. An image takes more memory than a word because it contains more details that need to be stored.