// For Arduino Uno, Digital Pin 13 is connected to PB5 (Port B, Bit 5) on the ATmega328P microcontroller.
// DDRB: Data Direction Register for Port B. Controls whether a pin is INPUT (0) or OUTPUT (1).
// PORTB: Port B Data Register. Controls the HIGH (1) or LOW (0) state of an OUTPUT pin.

void setup() {
  // Set Digital Pin 13 (PB5) as an OUTPUT.
  // We do this by setting the 5th bit of the DDRB register to 1.
  DDRB |= (1 << PB5); // |= is bitwise OR assignment. (1 << PB5) creates a bitmask with only PB5 set.
                      // This effectively sets PB5 to 1 without affecting other bits in DDRB.
}

void loop() {
  // Turn the LED on (HIGH).
  // We do this by setting the 5th bit of the PORTB register to 1.
  PORTB |= (1 << PB5); // Sets PB5 to HIGH.
  delay(500);           // Wait for 500 milliseconds (using a standard Arduino delay for simplicity)

  // Turn the LED off (LOW).
  // We do this by clearing the 5th bit of the PORTB register to 0.
  PORTB &= ~(1 << PB5); // &= ~ is bitwise AND NOT assignment. It clears the specified bit.
                        // ~(1 << PB5) creates a mask with all bits set EXCEPT PB5.
                        // This effectively sets PB5 to LOW without affecting other bits in PORTB.
  delay(500);           // Wait for 500 milliseconds
}