Which function is used to read input from the user in an Arduino sketch?

• A. Serial.print
• B. Serial.println
• C. Serial.available
• D. None of the other

Answer: (C)

When handling input from the serial port in an Arduino sketch, you first check whether data has arrived in the input buffer. The function that reports this is Serial.available; it returns how many bytes are waiting to be read. If the result is greater than zero, you can then read the data with Serial.read (for byte by byte) or other reading functions to get a string or sequence of bytes. The Serial.print and Serial.println functions, on the other hand, are for sending data out to the host, not for reading input. So Serial.available is the right choice here because it tells you there is input ready to be read, which is the necessary step before actually retrieving the user’s input.