Help with arduino and button

Projects Programming
2

look this over

const byte PinLed = 13;
const byte PinBut = A0;
      byte butState;

boolean run;

const unsigned long OneSec = 1000;
      unsigned long msec0;

void loop () {
    unsigned long msec = millis ();

    if (run && msec - msec0 >= OneSec) {
        msec0 = msec;
        digitalWrite (PinLed, ! digitalRead (PinLed));
        Serial.println ("run");
    }

    byte but = digitalRead (PinBut);
    if (butState != but)  { // changed
        butState = but;
        delay (20);         // debounce

        if (LOW == but)     // pressed
            run = ! run;
    }
}

void setup ()
{
    Serial.begin (9600);

    pinMode (PinLed, OUTPUT);
    pinMode (PinBut, INPUT_PULLUP);
    butState = digitalRead (PinBut);
}