// code to print prime numbers from 1-10

#include <stdint.h>

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

uint8_t seg[10] = {
    0x3F,  // 0
    0x06,  // 1
    0x5B,  // 2
    0x4F,  // 3
    0x66,  // 4
    0x6D,  // 5
    0x7D,  // 6
    0x07,  // 7
    0x7F,  // 8
    0x6F   // 9
};

uint8_t prime[] = {2, 3, 5, 7};

void delay1sec(void){
    TCNT1 = 0;
    TCCR1A = 0x00;
    TCCR1B = 0x05;
    while (TCNT1 < 15625);
    TCCR1B = 0x00;
}

int main(void){
    DDRA = 0x7F;

    while (1){
        for (uint8_t i = 0; i < 4; i++){
            PORTA = seg[ prime[i] ];
            delay1sec();
        }
    }
}