Arduino Print Statements and Comments

Getting Started with Arduino Print Statements

Print Statements and Comments

Are you ready to take your Arduino programming skills to the next level? Our comprehensive guide on Arduino print statements and comments is here to help you become a proficient Arduino programmer. Whether you’re a beginner or an experienced maker, understanding the power of print statements and the art of commenting code effectively is essential for crafting robust and maintainable Arduino projects.

Print Statements

In Arduino programming, “print statements” are used to send data or information to the serial monitor, which is a tool that allows you to monitor and interact with your Arduino board through your computer. Print statements are commonly used for debugging and testing purposes to view the values of variables, sensor readings, or other information your Arduino code generates.

The two primary functions used for sending data to the serial monitor in Arduino are Serial.print() and Serial.println():

  • Serial.print(): This function is used to print data to the serial monitor without adding a newline character at the end. It allows you to display multiple pieces of information on the same line.
  • Serial.println(): This function is similar to Serial.print(), but it also adds a newline character (“\n”) at the end, which moves the cursor to the next line in the serial monitor.

After including these statements in your Arduino code, you can open the Arduino IDE, upload your code to the Arduino board, and open the serial monitor (Tools > Serial Monitor) to see the output.

Hello World!

“Hello, World!” is a simple, traditional, and often the first program that people write when learning a new programming language or environment. The purpose of a “Hello, World!” program is to verify that the basic setup of a programming environment is correct and that you can write, compile, and execute code successfully.

Typically, a “Hello, World!” program does nothing more than display the text “Hello, World!” on the screen or console.

Serial.print("Hello World");

The Serial Monitor

The Serial Monitor is a crucial tool in the Arduino Integrated Development Environment (IDE) that allows you to interact with your Arduino board and view output from your Arduino sketches (programs) through your computer’s USB connection. It’s especially useful for debugging and monitoring the behavior of your Arduino projects.

Here’s an explanation of the key features and functions of the Serial Monitor in Arduino:
Opening the Serial Monitor:

To open the Serial Monitor in the Arduino IDE, go to the “Tools” menu and select “Serial Monitor” (or use the keyboard shortcut Ctrl+Shift+M or Cmd+Shift+M on Mac). This will open a separate window where you can interact with your Arduino board.

Baud Rate:

The Serial Monitor allows you to set the baud rate, which is the communication speed between your computer and the Arduino board. The baud rate in your sketch (Serial.begin()) and in the Serial Monitor must match for proper communication. The most common baud rate is 9600, but other values are possible depending on your sketch settings.

Sending Data to the Arduino:

You can use the input field at the top of the Serial Monitor window to send data to your Arduino. This is useful for sending commands or parameters to your Arduino sketch when it’s running. Just type your message and click the “Send” button (or press Enter).

Receiving Data from the Arduino:

The main area of the Serial Monitor displays the data received from the Arduino board. This is where you’ll see the output of Serial.print() and Serial.println() statements in your sketch. Each message from the Arduino is displayed as a separate line.

Line Ending Options:

You can select different line-ending options (e.g., “No line ending,” “Newline,” “Carriage return,” etc.) in the drop-down menu at the bottom of the Serial Monitor window. This setting determines how the input data you send to the Arduino is terminated.

Clear Button:

The “Clear” button allows you to clear the contents of the Serial Monitor window if it becomes cluttered with data.


The “Auto-scroll” option, when enabled, automatically scrolls the Serial Monitor window to display the latest data at the bottom.

Logging Data:

You can log data from the Serial Monitor to a text file by clicking the “Save” button. This is helpful for recording and analyzing data from your Arduino projects.

Initialize Serial Communication:

In the setup() function of your Arduino sketch, initialize the serial communication using the Serial.begin() function. You specify the baud rate as an argument to this function. The most common baud rate is 9600, but it should match the baud rate set in the Serial Monitor.

Writing Your First Arduino Program

Open your IDE and copy the following code to a new sketch:

void setup() {
  // put your setup code here, to run once:
  Serial.print("Hello World!");

void loop() {
  // put your main code here, to run repeatedly:

  • Click Verify to test your code is free of errors. This will only test your code for syntax errors, not spelling mistakes.
  • Now, click the Upload icon, you will now be prompted to save your code. Name it helloWorld and click Save.
  • Once the code has finished uploading, click the Serial Monitor icon and make sure its set to 9600 baud rate.
hello World

Well done that’s your first program written and running successfully. Easy, wasn’t it?


Arduino Comments, like in many other programming languages, are used to add explanations, notes, or documentation within your code. Comments are ignored by the compiler and have no impact on the program’s functionality; they exist solely for the benefit of programmers who read and maintain the code. Here’s a brief explanation of comments in Arduino:

Single-Line Comments:

In Arduino, you can create single-line comments using two forward slashes (//). Anything following // on the same line is considered a comment and is ignored by the compiler.

void loop() {
// Send "Hello, World!" to the Serial Monitor
Serial.println("Hello, World!");
delay(1000); // Wait for 1 second

Multi-Line Comments:

Arduino also supports multi-line comments, which are enclosed between /* and */. Anything between these delimiters is treated as a comment and is ignored by the compiler. Multi-line comments are typically used for longer explanations or comments that span multiple lines. For example:

This is a multi-line comment.
It can span multiple lines and is useful
for providing detailed explanations.
int sensorValue = analogRead(A0);

Commenting Out Code:

You can also use comments to temporarily disable or “comment out” lines of code that you don’t want to be executed. This is useful for testing or debugging purposes. For instance:

// int sensorValue = analogRead(A0); // Commented out for testing

By adding // before the line, the code is effectively deactivated, but you can easily re-enable it by removing or modifying the comment.


Print Statements can help monitor the behavior of your Arduino program, check the values of variables, and troubleshoot any issues in your code.

The Serial Monitor is an essential tool for debugging and monitoring your Arduino projects. It allows you to see the values of variables, debug code errors, and interact with your Arduino sketch in real-time, making it easier to develop and test your projects effectively.

Comments are an essential part of writing clean and maintainable code in Arduino, as they help you and others understand the purpose and functionality of different parts of your program. They also facilitate debugging and troubleshooting by providing context and explanations for the code you’ve written.


If you don’t already own any Arduino hardware, we highly recommend purchasing the Elegoo Super Starter Kit. This kit has everything you need to start programming with Arduino.

You can find out more about this kit here: Elegoo Super Starter Kit

Happy Tinkering!

Luke Barber

Hello, fellow tech enthusiasts! I'm Luke, a passionate learner and explorer in the vast realms of technology. Welcome to my digital space where I share the insights and adventures gained from my journey into the fascinating worlds of Arduino, Python, Linux, Ethical Hacking, and beyond. Armed with qualifications including CompTIA A+, Sec+, Cisco CCNA, Unix/Linux and Bash Shell Scripting, JavaScript Application Programming, Python Programming and Ethical Hacking, I thrive in the ever-evolving landscape of coding, computers, and networks. As a tech enthusiast, I'm on a mission to simplify the complexities of technology through my blogs, offering a glimpse into the marvels of Arduino, Python, Linux, and Ethical Hacking techniques. Whether you're a fellow coder or a curious mind, I invite you to join me on this journey of continuous learning and discovery.

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