Reading a button

/*

 Button

 Turns on and off a light emitting diode(LED) connected to digital pin 13,

 when pressing a pushbutton attached to pin 2.

 The circuit:

 - LED attached from pin 13 to ground through 220 ohm resistor

 - pushbutton attached to pin 2 from +5V

 - 10K resistor attached to pin 2 from ground

 - Note: on most Arduinos there is already an LED on the board

   attached to pin 13.

 created 2005

 by DojoDave <http://www.0j0.org>

 modified 30 Aug 2011

 by Tom Igoe

 This example code is in the public domain.

 https://docs.arduino.cc/built-in-examples/digital/Button/

*/

// constants won't change. They're used here to set pin numbers:

const int buttonPin = 2;  // the number of the pushbutton pin

const int ledPin = 13;    // the number of the LED pin

// variables will change:

int buttonState = 0;  // variable for reading the pushbutton status

void setup() {

 // initialize the LED pin as an output:

 pinMode(ledPin, OUTPUT);

 // initialize the pushbutton pin as an input:

 pinMode(buttonPin, INPUT);

}

void loop() {

 // read the state of the pushbutton value:

 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);

 }

}