#include <util/delay.h>

// Macros that facilitate bitwise operation
#define READ_BIT(destiny, bit)      (((destiny) >> (bit)) & 1)
#define SET_BIT(destiny, bit)       (destiny) = (destiny) | (1 << (bit))
#define CLEAR_BIT(destiny, bit)     (destiny) = (destiny) & ~(1 << (bit))
#define WRITE_BIT(destiny, value)   (destiny) = (value) ? CLEAR_BIT((destiny), (bit)) : SET_BIT((destiny), (bit))
#define TOGGLE_BIT(destiny, bit)    (destiny) = READ_BIT((destiny), (bit)) ? CLEAR_BIT((destiny), (bit)) : SET_BIT((destiny), (bit))

// Macro to make this cast more readable. C++ casts is more faster and safer.
#define REFERENCE_CAST              *reinterpret_cast<uint8_t*>

// Using a reference instead of a pointer makes the code safer.
#define PORTB                       REFERENCE_CAST(0x25)
#define DDRB                        REFERENCE_CAST(0x24)
#define PINB                        REFERENCE_CAST(0x23)

int main(void){
  SET_BIT(DDRB, 5); // Setting pin 13 as output
  for(;;){
    TOGGLE_BIT(PORTB, 5); // Toggling pin 13 state
    _delay_ms(1000);  // Delay
  }
}