//if external PB0 is pressed leds 0,3,4,7 will turn on

#include <stdint.h>

#define DDRA   (*(volatile uint8_t*)0x21)
#define PORTA  (*(volatile uint8_t*)0x22)

#define PINB   (*(volatile uint8_t*)0x23)
#define DDRB   (*(volatile uint8_t*)0x24)

int main(void){
    DDRA = 0xFF;   
    DDRB = 0x00;   

    while(1){
        if (PINB & (1 << 0)) {     // PB0 pressed (external pull-down)
            PORTA = 0x99;          // LEDs 0,3,4,7 ON
        } else {
            PORTA = 0x00;          
        }
    }
}