while (1) {
    PORTD = 0xFF; // Turn on LED.
    _delay_ms(500);

    PORTD = 0x00; // Turn of LED.
    _delay_ms(500);
}

return 0;

3. Run commands below in your terminal:
  1. `avr-gcc -w -Os -DF_CPU=1000000UL -mmcu=atmega32 -c -o main.o main.c`
  2. `avr-gcc -w -mmcu=atmega32 main.o -o main`
  3. `avr-objcopy -O ihex -R .eeprom main main.hex`
  4. `sudo avrdude -F -V -c usbasp -p m32 -P usb -U flash:w:main.hex`