#4.5.2.1. 예제 

void setup() {

  pinMode(5, INPUT_PULLUP);

  pinMode(6, INPUT_PULLUP);

  pinMode(7, INPUT_PULLUP);

  pinMode(9, OUTPUT);

  pinMode(10, OUTPUT);

  pinMode(11, OUTPUT);

}

void loop() {

  if (digitalRead(5) == LOW) {

    analogWrite(11, 0);

    analogWrite(10, 0);

    analogWrite(9, 255);

  } else if (digitalRead(6) == LOW) {

    analogWrite(11, 0);

    analogWrite(10, 255);

    analogWrite(9, 0);

  } else if (digitalRead(7) == LOW) {

    analogWrite(11, 255);

    analogWrite(10, 0);

    analogWrite(9, 0);

  } else {

    analogWrite(11, 0);

    analogWrite(10, 0);

    analogWrite(9, 0);

  }

}