Extract the Nibble from an 8-bit Register

#include <stdio.h>
#include <cstdint>

unsigned char extractNibble(unsigned char reg, int pos) {
    // Write your code here
uint8_t mask=0x0F;
    if (pos==0){
mask &=reg;
return mask;
    }
 if(pos==1){
reg=(reg>>4);
mask &=reg;
return mask;
    }
}

int main() {
    unsigned char reg;
    int pos;
    scanf("%hhu %d", &reg, &pos);
    printf("%d", extractNibble(reg, pos));
    return 0;
}