Experiment 1: Basic counter

counter1.ino

// Declare variable to be used as a counter.
  // This has to be done outside `setup` and `loop` so that `counter` is visible
  // inside both functions
byte counter;

// The setup function runs once when you press reset or power the board
void setup() {
    // initialize counter
    counter = 0; 

    // Set pins 0-5 of Port C as outputs.
    DDRC = 0b00111111; // the prefix “0b” qualifies the number as binary
    PORTC = 0; // so all the LEDs are off initially
}

// The loop function runs repeatedly forever
void loop() {
    PORTC = counter;

    // increment counter
      // we could replace the next line with: counter1++;
      // or the previous line with PORTC = counter1++;
    counter = counter + 1;

   // Uncomment the following three lines for a modulus of 60: 
    // if (counter > 59) {
    //     counter = 0;
    // }

    delay(1000); // reduce the delay if you get bored waiting!
}