4_arduino_serial_EN.ino

void setup() {
  // put your setup code here, to run once:

  Serial.begin(9600); //Initialization serial communication at 9600 bauds(default setting)
  //The baud is a unit used to measure the speed of transmission of information

  Serial.println("Hello Steem !"); //Display a message (here it is: Hello Steem!) And then return to the line (because of the ln after the print)
}

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

  if (Serial.available() ) //If the condition between () is true then :
  {
    //If a message has been received do this
    Serial.print("Votre message: "); //Display a message without returning to the line
    Serial.println(Serial.readString());  // Read the received message and display it on the monitor
  }
  else
  {
   // If nothing is received do this (you can put here what you want)
    //It is not mandatory to put an else (if not) after an if if you do not need it
  }
}