Which function initiates serial communication on the Arduino?

• A. Serial.available()
• B. Serial.print()
• C. Serial.end()
• D. Serial.begin()

Answer: (D)

Starting serial communication on an Arduino requires configuring the UART and enabling the serial port. The function that does this is Serial.begin(baudrate). By calling Serial.begin with a chosen speed (for example, 9600 or 115200), you set up the hardware to communicate over the serial link and allow data to be sent and received. This setup is typically done once in the setup() function so the port is ready as soon as the program starts. After beginning, you can use Serial.print or Serial.println to send data, and you can use Serial.available to check how many bytes are ready to read and Serial.read to retrieve them. Serial.end exists to stop the serial communication, but it only matters after you’ve started it.