PINA, PINB

http://www.hackerschool.org/Sub_Html/HS_University/HardwareHacking/26.html

#include <avr/io.h>

int main(void)
{
    DDRA = 0xff;        //Output
    DDRB = 0x00;    //Input

    while(1)		
    {
        if(PINB & 0x01)
            PORTA = 0x01;
	else
	    PORTA = 0x00;
    }
}

PINB	0	0	0	0	0	0	0	1
0x01	0	0	0	0	0	0	0	0