Notes

// Pin 13 has an LED connected on most Arduino boards.
// give it a name:
int led = 13;
const int buttonPin = 4;
const int ledPin = 7;
int buttonState = 0;
// the setup routine runs once when you press reset:
void setup() {
// initialize the digital pin as an output.
pinMode(led, OUTPUT);
pinMode(ledPin, OUTPUT);
pinMode(buttonPin, INPUT);
}

// the loop routine runs over and over again forever:
void loop() {
digitalWrite(led, HIGH); // turn the LED on (HIGH is the voltage level)
delay(200); // wait for a second
digitalWrite(led, LOW); // turn the LED off by making the voltage LOW
delay(200); // wait for a second

buttonState = digitalRead(buttonPin);
// check if the pushbutton is pressed.
// if it is, the buttonState is HIGH:
if (buttonState == HIGH) {
// turn LED on:
digitalWrite(ledPin, HIGH);
} else {
// turn LED off:
digitalWrite(ledPin, LOW);
}


}