17. Extract the Nibble from an 8-bit Register

#include <stdio.h>

#define UPPER_NIBBLE(reg) (((reg) >> 4) & 0xf)
#define LOWER_NIBBLE(reg) ((reg) & 0xf)

unsigned char extractNibble(unsigned char reg, int pos) {
    return ((pos) ? UPPER_NIBBLE(reg) : LOWER_NIBBLE(reg)); 
}

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