#include <avr/io.h>

int main(void)
{
	char temp;
	unsigned int i,j;
	DDRA |= (1 << 3);//等效于DDRA = DDRA | (1 << 3);
	PORTA &= ~(1 << 3);//等效于PORTA = PORTA & 0b11110111;
	while(1)
	{
		PORTA ^= (1 << 3);//等效于PORTA = PORTA ^ (1 << 3);
		for(i = 0;i < 50;i ++)
		{
			for(j = 0;j < 1000;j ++);
		}
	}
}