Arduino is a virtual platform where anyone can utilize hardware and software easily as this is an open-source platform. The Arduino code is written in C++ but with some extra strategies and capacities.

The new Arduino learners come across many different types of errors. But troubleshooting these error codes can’t always be easy to do. The errors mostly occur when compiling the Arduino codes. It is shown at the bottom of the software known as Arduino IDE. The Arduino IDE can indicate where the error exists and suggest a solution. The “Was not declared in this scope” is the most common error people face when programming with Arduino. Here we’ll discuss what the error is and how to fix the error.

What is the “Was Not Declared in This Scope” Error in Arduino?

When there is any undeclared variable, the Arduino IDE can’t identify any variable or can’t process any instruction or loop. This means the instructions Arduino gave fail to process the code you are trying to compile.

So, if you do not declare a variable before assigning a value for the Arduino IDE to process, it gives you the error “was not declared in this scope”.

What Causes the “Was Not Declared in This Scope” Error and How to Solve it?

Solving this is a very simple method. All you need to do is declare the variable. Here we will show you what causes this error and how you can solve it.

Reasons Why the Error Occurs

Here’s an example of an operation being performed and Arduino IDE showing us the error:

Step 1: This is an Arduino code that performs a simple addition operation:

Step 2: But as you can see, we have not declared the value of “b”. So, the Arduino IDE shows an error:

Step 3: And here you’ll see that the Arduino IDE has pointed out that variable “b” was not declared:

Step 4: The Arduino IDE will highlight the variable that is causing the error to happen:

How to Solve the Error

As stated before, all you need is to declare the variable and you’ll be good to go. Here’s how:

Step 1: Remove the error by assigning a value to declare the variable:

Here we have declared the variable by assigning the value of “b”.

Step 2: After successfully compiling the code, Arduino IDE now shows the correct completion message:

Step 3: And the serial monitor now shows the output of the code:

Frequently Asked Questions (FAQs)

What is a scope of a variable?

Simply put, the scope of a variable is its lifetime in the program. This simply means that in the whole program where the variable is declared, used, and can be modified, the scope of a variable is the block of code.

What are the three types of variable scope?

The three types of variables are:

1. Local variable.
2. Global variable.
3. Static variable.

Conclusion

While compiling the code in Arduino IDE, you might encounter several different errors. But these can be fixed by simply paying attention and avoiding mistakes. We hope you have found the solution to the error through us. Please let us know if there are any additional issues you are facing.