#include <avr/io.h>

#define SET(REGISTER, BIT)		REGISTER |= 1 << BIT
#define CLEAR(REGISTER, BIT)	REGISTER &= ~(1 << BIT)
#define TEST(REGISTER, BIT)		REGISTER & 1 << BIT
#define TOGGLE(REGISTER, BIT)	REGISTER ^= 1 << BIT

#define D1 0
#define D2 1
#define D3 2
#define D4 4

int main()
{
    // DDRx : select direction of the pin
    //      - 1 = output (pull-up off)
    //      - 0 = input
    // PORTx :
    //      if DDRx = 1 (output mode) :
    //      - 1 = HIGH (5V)
    //      - 0 = LOW (0V)
    //      if DDRx = 0 (input mode) : 
    //      - 1 = pull-up on
    //      - 0 = pull-up off
    // PINx : 


    SET(DDRB, D1);		// make PB0 as OUTPUT (pullup is off)
    CLEAR(PORTB, D1);	// make PB0 as HIGH (LED turns ON)

    // SET(DDRB, D2);		// make PB1 as OUTPUT (pullup is off)
    // CLEAR(PORTB, D2);	// make PB1 as LOW (LED turns OFF)

    // CLEAR(DDRB, D3);		// make PB2 as INPUT
    // SET(PORTB, D3);		// make PB2 pullup on

    // CLEAR(DDRB, D4);		// make PB4 as INPUT
    // CLEAR(PORTB, D4);	// make PB4 pullup off

    return 0;
}