Two buttons, one LED, on an Arduino Uno

// Two buttons, one LED: the left button turns it on, the right one off.
//
//   pin 5   the LED, through 220 ohm to GND
//   pin 9   button A (on), its other leg to GND
//   pin 8   button B (off), its other leg to GND
//
// Neither button has a resistor. INPUT_PULLUP switches on the chip's own
// pull-up, which holds the pin at 5 V until the button joins it to ground.
// So a pin reads HIGH while its button is up and LOW while it is held.
//
// The LED stays the way the last button left it. That is the difference from
// a button wired straight to an LED: the board remembers.

const int LED_PIN = 5;
const int BUTTON_ON = 9;
const int BUTTON_OFF = 8;

bool lit = false;

void setup() {
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUTTON_ON, INPUT_PULLUP);
  pinMode(BUTTON_OFF, INPUT_PULLUP);
  Serial.begin(9600);
  Serial.println("Mokxi Uno: button A on pin 9 lights the LED, button B on pin 8 puts it out");
}

void loop() {
  if (digitalRead(BUTTON_ON) == LOW && !lit) {
    lit = true;
    digitalWrite(LED_PIN, HIGH);
    Serial.println("on");
  }
  if (digitalRead(BUTTON_OFF) == LOW && lit) {
    lit = false;
    digitalWrite(LED_PIN, LOW);
    Serial.println("off");
  }
  delay(5);
}