/* Program 4-3: Echo the received characters of the Serial port
 * The Arduino echo back the received character.
 */

void setup() { 
    Serial.begin(9600);    /* initialize Serial and set the Baud rate to 9600 */
} 

void loop() {
    while (!Serial.available()) { }    /* wait until a char is available */
    char c = Serial.read();            /* read the character */
    Serial.write(c);                   /* echo the character received */
}